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10 tháng 7 2017

Đáp án:

- “until the age of 15” là cụm trạng ngữ.

- Động từ “expects” ở thì hiện tại nên dùng “It is”

- Công thức: It + is + adverbial phrase + that + S + V.

=> It is until the age of 15 that dating is not allowed in Central and South America.

Tạm dịch: Chính cho đến khi 15 tuổi việc hẹn hò không được cho phép ở Trung Mỹ và Nam Mỹ.

Đáp án cần chọn là: A

20 tháng 2 2018

Đáp án A

Trong Mệnh đề quan hệ, khi đại từ quan hệ thay thế cho danh từ chỉ tên riêng (Binh Thuan) thì nó được cho là Mệnh đề quan hệ không xác định. Khi này phần thông tin được thêm vào sẽ được ngăn cách bởi 2 dấu phẩy.

Dịch: Tỉnh Bình Thuận, nằm ở vùng duyên hải Nam Trung Bộ, nổi tiếng về những cảnh quan và bãi biển đẹp.

Ex5. Choose the best answer. Brazil, the largest country in South America and the fifth largest country in the world, is located in the Eastern half of South America. The people of Brazil are famous for their outgoing, friendly, and fun- loving nature. Brazilian women are considered to be among the best dressed in the world.Brazil is a federal republic with 23 states. The capital city is Brasilia. Portuguese is the official language and it is spoken with a distinct Brazilian accent. Brazil has...
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Ex5. Choose the best answer.

Brazil, the largest country in South America and the fifth largest country in the world, is located in the Eastern half of South America. The people of Brazil are famous for their outgoing, friendly, and fun- loving nature. Brazilian women are considered to be among the best dressed in the world.

Brazil is a federal republic with 23 states. The capital city is Brasilia. Portuguese is the official language and it is spoken with a distinct Brazilian accent. Brazil has a population of over one hundred and thirty-eight million, which is made up of people of many different races and ethnic group.

A number of industrial products are produced in Brazil, including cars, chemicals, ships, machines, and military weapons. Mining is also an important industry. Agriculture is another important industry. Many crops are exported, including coffee, cotton, soybeans, sugar, cocoa, rice, corn and fruit.

1.  Where is Brazil ? - It is located in _______.

A.  Eastern half of South America                   B. Eastern half of America C. South America                                            D. Western half of South America

2.  What is Brazil's official language?

A.  English                   B. Brazilian                  C. Portuguese             D. Portugal

3.  What is the population of Brazil?

A.  Around 158 million                                     B. Over 138 million

                C. 128 million                                                  D. Not mentioned

4.  What are the people of Brazil famous for?

A.  Their outgoing, friendly, and fun- loving nature.

B.  Their cars, chemicals and ships.

C.  Their machines, and military weapons.

D.  Their coffee, cotton, soybeans, sugar, cocoa, rice, corn and fruit.

3
11 tháng 2 2022

1.  Where is Brazil ? - It is located in _______.

A.  Eastern half of South America                   B. Eastern half of America C. South America                                            D. Western half of South America

2.  What is Brazil's official language?

A.  English                   B. Brazilian                  C. Portuguese             D. Portugal

3.  What is the population of Brazil?

A.  Around 158 million                                     B. Over 138 million

                C. 128 million                                                  D. Not mentioned

4.  What are the people of Brazil famous for?

A.  Their outgoing, friendly, and fun- loving nature.

B.  Their cars, chemicals and ships.

C.  Their machines, and military weapons.

 

D.  Their coffee, cotton, soybeans, sugar, cocoa, rice, corn and fruit.

 

11 tháng 2 2022

1A

2C

3B

4A

VI. Read the text below and decide which answer (A, B, C or D) best fits each question;Brazil, the largest country in South America and the fifth largest country in the world, is located in the eastern half of South America. The people of Brazil are famous for their outgoing, friendly, and fun-loving nature. Brazilian women are considered to be among the best dressed in the world. Brazil is a federal republic with 23 states. The capital city is Brasilia. Portuguese is the official language and...
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VI. Read the text below and decide which answer (A, B, C or D) best fits each question;

Brazil, the largest country in South America and the fifth largest country in the world, is located in the eastern half of South America. The people of Brazil are famous for their outgoing, friendly, and fun-loving nature. Brazilian women are considered to be among the best dressed in the world. Brazil is a federal republic with 23 states. The capital city is Brasilia. Portuguese is the official language and it is spoken with a distinct Brazilian accent. Brazil has population of over 138 million, which is made of people of many different races and ethnic groups. A number of industrial products are produced in Brazil, including cars, chemicals, ships, machines, and military weapons. Mining is also an important industry. Agriculture is another important industry. Many crops are exported including coffee (Brazil is the largest coffee grower in the world), cotton, soybeans, sugar, cocoa, rice, corn and fruit.

1. Who are considered to be among the best dressed in the world?

A. Brazilian men                     B. Brazilians                C. Americans              D. Brazilian women

2. How are the people of Brazil?

A. Outgoing, famous, and natural.                 B. Outgoing, friendly, and natural.

C. Outgoing, friendly, and fun-loving.           D. Famous, friendly, and fun-loving.

3. The word “rice” in line 11 is closest in meaning to            .

A. a kind of vegetables           B. a kind of grains      C. a kind of meat          D. a kind of drinks

4. What is the most significant agricultural product in Brazil?

A. cocoa                                  B. coffee                     C. corn                        D. cotton

VII. Choose one suitable word which best fits each gap of the passage.(3 points)

            Music is an art that puts sounds together in a way that people like or find (1) …….. Most music includes people (2) …….. their voice or (3) …… musical instruments, such as a piano, a guitar, or drums. People can enjoy music by (4) ……. to it. They can go to the (5) …….to hear musicians perform. Classical music is usually (6) ………in concert halls, but sometimes huge ( 7) ……… are organized in which it is performed outside, in a field or a stadium, like pop festivals. People can listen to music on CDs, computers, Ipods, televisions, radios, cassettes/recordplayers and even (8) …… People can learn to play a musical instrument such as the piano, the guitar, the bass, the trumpet, the drums, or the flute. Anyone can make up his or her own (9) ….. of music. It is not difficult to (10) …… simple  songs  or melodies, but it is easier for those who can play an instrument themselves.

1.      A. interest                  B. interesting               C.interested                D. interests

2.      A. saying                   B. thinking                  C. singing                    D. telling

3.      A. playing                  B. singing                    C. doing                      D. making

4.      A. writing                  B. typing                     C. listening                  D. chatting

5.      A. concerts                B. plays                       C. dramas                    D. movies

6.      A. done                      B. performed               C. read                                    D. made

7.      A. songs                     B. meetings                 C. festivals                  D. classes

8.      A. books                    B. mobiles                   C. songs                      D. poems

9.      A. piece                     B. unit                         C. part                         D. lesson

10.  A. do                                     B. compose                 C. say                          D. make          

VIII. Fill in each numbered blank with ONE suitable word. (3 points)

                                                CHRISTMAS IN ENGLAND

            In England, children get their presents (1) ............ Christmas Eve, the 24th of December. Father Christmas comes at (2) ........when everyone is asleep. His (3) ........... can fly and takeshim from house to house to ( 4) ........all the gifts. They land on the roofs of the houses and then Father Christmas (5) .......down the chimney to leave the presents (6) .........the Christmas tree. In the morning of Christmas Day, the 25th of December, children usually get up very early to unwrap their (7) .......... Then they have plenty of time to play with their new toys. Christmas dinner is served (8) ......... the early afternoon. Most people eat turkey, sprouts and loads of other vegetables, not forgetting Christmas(9) .......... The 26th of December is called Boxing Day. It has not always been a holiday. People used to go back to work on that day where their bosses gave them little Christmas presents in small boxes. That is (10) .......... the day is called Boxing Day.

Write your answers here:

1 ………….

2.....................

3.....................

4......................

5......................

6 ………….

7....................

8.....................

9.....................

10.....................

2
17 tháng 8 2021

VI. Read the text below and decide which answer (A, B, C or D) best fits each question;

Brazil, the largest country in South America and the fifth largest country in the world, is located in the eastern half of South America. The people of Brazil are famous for their outgoing, friendly, and fun-loving nature. Brazilian women are considered to be among the best dressed in the world. Brazil is a federal republic with 23 states. The capital city is Brasilia. Portuguese is the official language and it is spoken with a distinct Brazilian accent. Brazil has population of over 138 million, which is made of people of many different races and ethnic groups. A number of industrial products are produced in Brazil, including cars, chemicals, ships, machines, and military weapons. Mining is also an important industry. Agriculture is another important industry. Many crops are exported including coffee (Brazil is the largest coffee grower in the world), cotton, soybeans, sugar, cocoa, rice, corn and fruit.

 

(Brazil, quốc gia lớn nhất ở Nam Mỹ và là quốc gia lớn thứ năm trên thế giới, nằm ở nửa phía đông của Nam Mỹ. Người dân Brazil nổi tiếng với bản tính hòa đồng, thân thiện và vui vẻ. Phụ nữ Brazil được coi là một trong những người mặc đẹp nhất thế giới. Brazil là một nước cộng hòa liên bang với 23 tiểu bang. Thành phố thủ đô là Brasilia. Tiếng Bồ Đào Nha là ngôn ngữ chính thức và nó được nói với một giọng Brazil riêng biệt. Brazil có dân số hơn 138 triệu người, bao gồm những người thuộc nhiều chủng tộc và dân tộc khác nhau. Một số sản phẩm công nghiệp được sản xuất ở Brazil, bao gồm ô tô, hóa chất, tàu thủy, máy móc và vũ khí quân sự. Khai thác cũng là một ngành công nghiệp quan trọng. Nông nghiệp là một ngành quan trọng khác. Nhiều loại cây trồng được xuất khẩu bao gồm cà phê (Brazil là nước trồng cà phê lớn nhất trên thế giới), bông, đậu nành, đường, ca cao, gạo, ngô và trái cây.)

 

1. Who are considered to be among the best dressed in the world?

A. Brazilian men                     B. Brazilians                C. Americans              D. Brazilian women

2. How are the people of Brazil?

A. Outgoing, famous, and natural.                 B. Outgoing, friendly, and natural.

C. Outgoing, friendly, and fun-loving.           D. Famous, friendly, and fun-loving.

3. The word “rice” in line 11 is closest in meaning to            .

A. a kind of vegetables           B. a kind of grains      C. a kind of meat          D. a kind of drinks

4. What is the most significant agricultural product in Brazil?

A. cocoa                                  B. coffee                     C. corn                        D. cotton

 

17 tháng 8 2021

VII. Choose one suitable word which best fits each gap of the passage.(3 points)

            Music is an art that puts sounds together in a way that people like or find (1) …….. Most music includes people (2) …….. their voice or (3) …… musical instruments, such as a piano, a guitar, or drums. People can enjoy music by (4) ……. to it. They can go to the (5) …….to hear musicians perform. Classical music is usually (6) ………in concert halls, but sometimes huge ( 7) ……… are organized in which it is performed outside, in a field or a stadium, like pop festivals. People can listen to music on CDs, computers, Ipods, televisions, radios, cassettes/recordplayers and even (8) …… People can learn to play a musical instrument such as the piano, the guitar, the bass, the trumpet, the drums, or the flute. Anyone can make up his or her own (9) ….. of music. It is not difficult to (10) …… simple  songs  or melodies, but it is easier for those who can play an instrument themselves.

1.      A. interest                  B. interesting (thú vị)              C.interested                D. interests

2.      A. saying                   B. thinking                  C. singing                    D. telling

3.      A. playing                  B. singing                    C. doing                      D. making

4.      A. writing                  B. typing                     C. listening                  D. chatting

5.      A.d (buổi hòa nhạc)                B. plays                       C. dramas                    D. movies

6.      A. done                      B. performed (biểu diễn)              C. read                                    D. made

7.      A. songs                     B. meetings                 C. festivals                  D. classes

8.      A. books                    B. mobiles                   C. songs                      D. poems

9.      A. piece  (of music: mẩu nhạc)                   B. unit                         C. part                         D. lesson

10.  A. do                                     B. compose (sáng tác)                 C. say                          D. make          

VIII. Fill in each numbered blank with ONE suitable word. (3 points)

                                                CHRISTMAS IN ENGLAND

            In England, children get their presents (1) ......on...... Christmas Eve, the 24th of December. Father Christmas comes at (2) ...night.....when everyone is asleep. His (3) ......reindeer..... can fly and take him from house to house to ( 4) ...give.....all the gifts. They land on the roofs of the houses and then Father Christmas (5) ...climbs....down the chimney to leave the presents (6) ...under......the Christmas tree. In the morning of Christmas Day, the 25th of December, children usually get up very early to unwrap their (7) ...presents....... Then they have plenty of time to play with their new toys. Christmas dinner is served (8) ..in....... the early afternoon. Most people eat turkey, sprouts and loads of other vegetables, not forgetting Christmas(9) ...pudding....... The 26th of December is called Boxing Day. It has not always been a holiday. People used to go back to work on that day where their bosses gave them little Christmas presents in small boxes. That is (10) ...why....... the day is called Boxing Day.

13 tháng 12 2017

Kiến thức: Từ vựng

Giải thích:

It is not until … that…: Mãi cho đến khi … thì …

only when + S + V: chỉ khi

tobe allowed to do something: được pháp làm gì

Tạm dịch: Chỉ đến khi một cô gái Việt Nam đủ 18 tuổi thì cô ấy mới được phép kết hôn một cách hợp pháp.

   A. Một cô gái Việt Nam không được phép kết hôn hợp pháp chỉ khi cô ấy 18 tuổi.                          B. Một cô gái Việt Nam chỉ được phép kết hôn hợp pháp khi cô ấy 18 tuổi.

   C. Sự chấp nhận về mặt pháp lý cho một cô gái Việt Nam kết hôn sẽ được cấp trong 18 năm.          D. Họ không bao giờ cho phép một cô gái Việt Nam kết hôn hợp pháp khi cô ấy 18 tuổi.

Câu A, C, D sai về nghĩa.

Chọn B 

III. Read the passage below and answer each of questions Tropical rain forests are found in Amazon region of south America, central America, Africa, and South and Southeast Asia. Rain forests are very important to the world’s climate. The Amazon rain forest alone receives about 30 to 40 % of the total rainfall on the earth and products about the same percentage of the world’s oxygen. Some scientists believe that the decreasing size of rain forests will affect the climate on the earth, making it...
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III. Read the passage below and answer each of questions
Tropical rain forests are found in Amazon region of south America, central America, Africa, and South and Southeast Asia. Rain forests are very important to the world’s climate. The Amazon rain forest alone receives about 30 to 40 % of the total rainfall on the earth and products about the same percentage of the world’s oxygen. Some scientists believe that the decreasing size of rain forests will affect the climate on the earth, making it uncomfortable or even dangerous for life. Saving our rain forests is an international problem. One country, or even a few countries can not solve the problem alone. The nations of the world must work together to find a solution before it is too late
1. Where are the rain forests found?
......................................................
2. How much percent of the would's oxygen do the Amozon rain forests produce?
......................................................................

3.How will the decrreasing size ò rain forests afect the climate on the earth?

.....................................................................................

4.Is saving our rain forests only a national problem?

...................................................................

1
23 tháng 6 2018

III. Read the passage below and answer each of questions
Tropical rain forests are found in Amazon region of south America, central America, Africa, and South and Southeast Asia. Rain forests are very important to the world’s climate. The Amazon rain forest alone receives about 30 to 40 % of the total rainfall on the earth and products about the same percentage of the world’s oxygen. Some scientists believe that the decreasing size of rain forests will affect the climate on the earth, making it uncomfortable or even dangerous for life. Saving our rain forests is an international problem. One country, or even a few countries can not solve the problem alone. The nations of the world must work together to find a solution before it is too late
1. Where are the rain forests found?

They are found in Amazon region of south America, central America, Africa, and South and Southeast Asia.
2. How much percent of the would's oxygen do the Amazon rain forest produce?

It produces about 30 to 40 percent of the world's oxygen.

3.How will the decrreasing size ò rain forests afect the climate on the earth?

It will make the climate on the Earth uncomfortable or even dangerous for life.

4.Is saving our rain forests only a national problem?

No, it isn't.

Day of the Dead – Mexico       Day of the Dead is celebrated on November 1 in Mexico, Ecuador, Guatemala and other parts of Central or South America. Families gather to pray to the souls of dead relatives, asking them to return for one night. People decorate altars in their homes and graveyards with food , candles, candy skulls and marigolds to welcome the souls back to Earth. Skeletons are displayed throughout cities, and people dressed as skeletons parade through the streets. Pan de los...
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Day of the Dead – Mexico

       Day of the Dead is celebrated on November 1 in Mexico, Ecuador, Guatemala and other parts of Central or South America. Families gather to pray to the souls of dead relatives, asking them to return for one night. People decorate altars in their homes and graveyards with food , candles, candy skulls and marigolds to welcome the souls back to Earth. Skeletons are displayed throughout cities, and people dressed as skeletons parade through the streets. Pan de los muertos (bread of the dead) is baked in the shape of skulls and crossbones, and a toy is hidden inside each loaf. The person who bites into the toy is said to have good luck. Day of the Dead is a time to celebrate and remember the lives of dead family members.

1.    Where and When is the Day of the Dead celebrated?

                                                                                                                                                

2.    What do families gather to pray for?

                                                                                                                                                

3.    What do people do to welcome the souls back to Earth?

                                                                                                                                                

4.    What is the custom with Pan de los muertos (bread of the dead)?

                                                                                                                                                

5.    What is the purpose of the Day of the Dead?

                                                                                                                                                

 

1
3 tháng 1 2022

1. Day of the Dead is celebrated on November 1.

2. Families gather to pray to the souls of dead relatives, asking them to return for one night.

3. People decorate altars in their homes and graveyards with food, candy skulls and marigolds to welcome the souls back to Earth.

4. Pan de los muertos is baked in the shape of skulls and crossbones, and a toy is hidden inside each loaf.

5. Day of the Dead is a time to celebrate and remember the lives of dead family members.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 13 to 50.           Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a...
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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 13 to 50.

          Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a radioactive substance such as carbon-14 has a known half-life, the amount of carbon-14 remaining in an object can be used to date that object.
          Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old.
          Carbon dating cannot be used effectively in dating objects that are older than 80,000 years. When objects are that old, much of the carbon-14 has already decayed into nitrogen-14, and the molecule amount that is left doesn’t provide a reliable measurement of age. In the case of older objects, other age-dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has

Which of the following is NOT true about carbon-14? 

A. It and nitrogen always exist in equal amounts in any substance

B. Its half-life is more than 5,000 years

C. It can decay into nitrogen-14. 

D. It is radioactive

1
23 tháng 5 2017

Đáp án A

Câu nào dưới đây KHÔNG ĐÚNG về carbon-14?

A. Nó và nitơ luôn tồn tại với số lượng bằng nhau trong bất kỳ chất nào.

B. Thời gian bán hủy của nó là hơn 5.000 năm.

C. Nó có thể phân rã thành nitơ-14.

D. Nó là chất phóng xạ.

Các đáp án B, C, D có thông tin được tìm thấy trong bài.

B + C- Dẫn chứng ở câu đầu đoạn 2: “Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14”- (Carbon-14 có thời gian bán hủy là 5,570 năm, có nghĩa là sau từng ấy năm, một nửa các nguyên tử carbon-14 đã bị phân hủy thành nitơ-14).

D- Dẫn chứng ở câu cuối đoạn 1: “Since a radioactive substance such as carbon-14 has a known half-life, […]” – (Bởi vì một chất phóng xạ thí dụ như carbon-14 có thời gian bán hủy như đã biết, […]) => Carbon-14 là một chất phóng xạ.

=> Còn lại đáp án A không đúng

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.          Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a...
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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.

          Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a radioactive substance such as carbon-14 has a known half-life, the amount of carbon-14 remaining in an object can be used to date that object.

          Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old. 

          Carbon dating cannot be used effectively in dating objects that are older than 80,000 years. When objects are that old, much of the carbon-14 has already decayed into nitrogen-14, and the molecule amount that is left doesn’t provide a reliable measurement of age. In the case of older objects, other age-dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has.

Which of the following is NOT true about carbon-14?

A. It and nitrogen always exist in equal amounts in any substance

B. Its half-life is more than 5,000 years

C. It can decay into nitrogen-14

D. It is radioactive

1
23 tháng 10 2018

Đáp án A

Câu nào dưới đây KHÔNG ĐÚNG về carbon-14? 

A. Nó và nitơ luôn tồn tại với số lượng bằng nhau trong bất kỳ chất nào. 

B. Thời gian bán hủy của nó là hơn 5.000 năm. 

C. Nó có thể phân rã thành nitơ-14. 

D. Nó là chất phóng xạ. 

Các đáp án B, C, D có thông tin được tìm thấy trong bài. 

B + C- Dẫn chứng ở câu đầu đoạn 2: “Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14”- (Carbon-14 có thời gian bán hủy là 5,570 năm, có nghĩa là sau từng ấy năm, một nửa các nguyên tử carbon-14 đã bị phân hủy thành nitơ-14). 

D- Dẫn chứng ở câu cuối đoạn 1: “Since a radioactive substance such as carbon-14 has a known half-life, […]” – (Bởi vì một chất phóng xạ thí dụ như carbon-14 có thời gian bán hủy như đã biết, […]) => Carbon-14 là một chất phóng xạ. 

=> Còn lại đáp án A không đúng.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.          Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a...
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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50.

         Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a radioactive substance such as carbon-14 has a known half-life, the amount of carbon-14 remaining in an object can be used to date that object.

        Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon-14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon-14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old.

        Carbon dating cannot be used effectively in dating objects that are older than 80,000 years. When objects are that old, much of the carbon-14 has already decayed into nitrogen-14, and the miniscule amount that is left doesn’t provide a reliable measurement of age. In the case of older objects, other age-dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has.

Which of the following is NOT true about carbon-14?

A. It and nitrogen always exist in equal amounts in any substance.

B. Its half-life is more than 5,000 years.

C. It can decay into nitrogen-14.

D. It is radioactive.

1
29 tháng 4 2019

Đáp án A.

Câu nào dưới đây KHÔNG ĐÚNG về carbon-14?

A. Nó và nitơ luôn tn tại với số lượng bằng nhau trong bất kỳ chất nào.

B. Thời gian bán hủy của nó là hơn 5.000 năm.

C. Nó có th phân rã thành nitơ-14.

D. Nó là chất phóng xạ.

Các đáp án B, C, D có thông tin được tìm thấy trong bài. B + C- Dn chứng ở câu đầu đoạn 2: “Carbon-14 has a half-life of 5, 570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14”: Carbon-14 có thời gian bán hủy 5.570 năm, có nghĩa là sau từng ẩy năm, một nửa các nguyên từ carbon-14 đã bị phân hủy thành nitơ-14. D- Dn chứng ở câu cuối đoạn 1 : “Since a radioactive substance such as carbon-14 has a known half-life, [...]”: Bởi vì một chất phóng xạ thí dụ như carbon-14 có thời gian bán hủy như đã biết, [...])Carbon-14 là một chất phóng xạ.

Còn lại đáp án A không đúng.