Virus, thường được viết là vi-rút (bắt nguồn từ tiếng Pháp virus /viʁys/),^[1] còn được gọi là siêu vi, siêu vi khuẩn hay siêu vi trùng,^[2] là một tác nhân truyền nhiễm chỉ nhân lên được khi ở bên trong tế bào sống của một sinh vật khác. Virus có thể xâm nhiễm vào tất cả các dạng sinh vật, từ động vật, thực vật cho tới vi khuẩn và vi khuẩn cổ.^[3] Kể từ bài viết đầu tiên của Dmitriy Iosifovich Ivanovsky năm 1892, mô tả về một dạng mầm bệnh không thuộc vi khuẩn mà lây nhiễm vào cây thuốc lá, và sự khám phá ra virus khảm thuốc lá của Martinus Beijerinck năm 1898,^[4] cho đến nay có khoảng 9,000 loại virus đã được miêu tả chi tiết,^[5] mặc dù vẫn còn có tới hàng triệu (hoặc tỷ) dạng virus khác nhau.^[6] Virus được tìm thấy ở hầu hết mọi hệ sinh thái trên Trái Đất và là dạng có số lượng nhiều nhất trong tất cả các thực thể sinh học.^[7][8] Khoa học nghiên cứu virus được biết với tên virus học (virology), một chuyên ngành phụ của vi sinh.

Bài này viết về virus trong sinh học và y học. Đối với virus ở lĩnh vực khác, xem Virus (định hướng).

Về bài viết giới thiệu chủ đề dễ tiếp cận hơn, ít mang nặng tính kĩ thuật, xem Giới thiệu về virus

Các phần tử (hay hạt) vi-rút (được gọi là virion hoặc vi-ri-ông) được tạo thành từ hai hoặc ba bộ phận: phần vật chất di truyền được tạo nên từ DNA hoặc RNA – những phân tử dài có mang thông tin di truyền, một lớp vỏ protein - được gọi với tên capsid - có chức năng bảo vệ hệ gen và một lớp vỏ bọc bên ngoài làm từ lipid mà bao bọc bên ngoài lớp vỏ protein khi virus ở ngoài tế bào (chỉ có trong một số trường hợp). Hình dạng của virus có sự khác nhau, từ dạng xoắn ốc hay khối hai mươi mặt đều đơn giản cho tới những cấu trúc phức tạp hơn. Một virus có kích thước trung bình vào khoảng 1/100 kích cỡ trung bình của một con vi khuẩn. Hầu hết virus đều quá nhỏ nên không thể quan sát trực tiếp dưới kính hiển vi quang học.

Nguồn gốc của virus trong lịch sử tiến hóa của sự sống không rõ ràng: một số có thể đã tiến hóa từ những plasmid – những đoạn DNA ngắn có khả năng di chuyển giữa các tế bào – trong khi số khác có thể đã tiến hóa từ vi khuẩn. Trong tiến hóa, virus là một phương tiện chuyển gen ngang quan trọng, góp phần gia tăng sự đa dạng di truyền.^[9] Virus được công nhận là một dạng sống bởi một số nhà khoa học, do chúng có mang vật chất di truyền, có thể sinh sản và tiến hóa thông qua quá trình chọn lọc tự nhiên. Tuy nhiên mặt khác chúng lại thiếu những đặc tính thiết yếu (như cấu trúc tế bào) - những điều được công nhận rộng rãi là cần thiết để được coi như sinh vật sống. Bởi vì chỉ có một số chứ không tất cả các phẩm chất cần thiết, nên virus được mô tả như "những sinh vật ở bên lề của sự sống". Tuy nhiên, virus chỉ có thể xâm nhập qua một số tế bào nhất định nhờ có giác bám (gai glycoprotein) của virus bám đặc hiệu lên thụ thể của tế bào chủ.^[10]

Virus lây lan theo nhiều cách; virus thực vật thường được truyền từ cây này sang cây khác qua những loài côn trùng hút nhựa cây như rệp vừng; trong khi virus động vật lại có thể được truyền đi nhờ những côn trùng hút máu. Những sinh vật mang mầm bệnh như vậy được gọi là những véc-tơ. Virus cúm lan truyền thông qua ho và hắt hơi. Norovirus và rotavirus, nguyên nhân chính của bệnh viêm dạ dày ruột siêu vi, lây lan qua đường phân-miệng và truyền từ người này sang người khác thông qua tiếp xúc, cũng như xâm nhập vào cơ thể qua thức ăn hay nước uống. HIV là một trong vài loại virus lây nhiễm thông qua quan hệ tình dục và tiếp xúc với máu bị nhiễm bệnh. Mỗi virus chỉ có thể xâm nhiễm vào một số dạng tế bào vật chủ nhất định, gọi là "biên độ vật chủ" (host range); biên độ này có thể rất hẹp hoặc rất rộng, tùy vào số lượng những sinh vật khác nhau mà virus có khả năng lây nhiễm.^[11]

Sự xâm nhập của virus trong động vật đã kích hoạt một phản ứng miễn dịch nhằm loại bỏ virus xâm nhiễm. Những phản ứng miễn dịch cũng có thể được tạo ra bởi vắc-xin, giúp tạo ra miễn dịch chủ động nhân tạo đối với một virus xâm nhiễm nhất định. Tuy nhiên, một số virus, bao gồm những loại gây ra AIDS và viêm gan siêu vi, lại có thể trốn tránh những phản ứng trên và gây ra sự nhiễm bệnh mãn tính. Đa phần các chất kháng sinh không có hiệu quả đối với virus, dù vậy cũng đã có những loại thuốc kháng virus (vắc-xin?) được phát triển.

^HT^

Sửa lại:

1 .there are many rooms in her apasmemt

2.is there a kitchen and a living room in the the house ?

3.my english looks and notbooks are in the table

4.there aren't a lot of people in my family

5.i live with my dad,my mum and my older brother

6.my brother and i are watching tv now

7.there isn't a computer in my bed room 

8.there are some celing fam on the class room

HT

thanks you

là seo pẹn???

ko hiểu

1. well

2. temperation

3. pain

4. stomache

5. headache

6. sickness

7. appointment

8. allergic

9. carefully

hải ngoại nha em

Overseas là gì vậy

=> ngoài nước, hải ngoại

????????????? ban tra loi kieu gi vay ko so bay nick a

ua tui lam gi ma ai k sai cho tui do

trả lời :

mk giúp đến đây

1,Nam is tall.Hung is taller

-->Hung.....is taller than Nam.........

2,Let's go campingin Suoi Mo

-->Why....don’t we go camping in Suoi Mo?.........

3,How much is a bottle of cooking oil?

-->How much does....a bottle of cooking oil cost?................

4,Nga usually walks to school

-->Nga.......usually goes to school on foot ...................

5,No body in my class in father than Hoang

-->Hoang is... the tallest in my class ..........

^HT^

Giúp tiếp:

6.When does she go to work?

7.Her favourite food is noodles.

8.How much are these apples?

9.It's a blue car.

10.It's never cold in summer.

11.Are there forty classrooms in Phong's school?

12.The red river is shorter than the mekong river.

13.How wide is the Great Wall?

14.Phuong is Nam's sister.

15.My father usually goes to work by car.

16.My class has forty students.

17.The house is in front òf the garden.

18.We usually go to school by bikes.

19.It's a big school.

20.She s apple juice.

HT~

1. She (not /want)…doesn't want ….any coffee. She (want)…wants …some tea.

2.     They (not/go)……don't go …..fishing in winter.

3.     I ()…… ………my English class very much.

4.     He usually (go)……goes …….to the library when he has free time.

5.     What……does ……Mrs. Brown (do) … …do….? – She’s a teacher.

6.     What……does …….your father often (do)……do …….in the evening?

7.     Look! The boy (climb) ……is  climbing…….. up a ladder.

8.     They (play)…play… …….volleyball every afternoon, but they (not/play)…aren't playing… ……badminton now.

9.     He (learn)…is learning… …. English and I (read)…am reading… …. a book now.

10.     He often (have)… has………coffee for breakfast.

11. What is the weather  today? It is cold.

12. He usually goes jogging in the morning.

13. He often goes swimming. He is going swimming at the moment.

14. My sister does aerobics every morning.

15. Lan goes to school six days a week.

16. We don't go swimming in the winter.

17. He often goes the movie on Sunday.

18. The students are doing their homework now.

19. My mother s iced tea.

20. He never goes camping because he doesn't have a tent. 

1. She (not /want)……doesn't want…….any coffee. She (want)……wants..…some tea.

2. They (not/go)………don't go………..fishing in winter.

3. I ()…….………my English class very much.

4. He usually (go)…….goes.…….to the library when he has free time.

5. What…….does……Mrs. Brown (do)……do.…….? – She’s a teacher.

6. What…….does…….your father often (do)……..do…….in the evening?

7. Look! The boy (climb) ……is climbing……….. up a ladder.

8. They (play)……play….…….volleyball every afternoon, but they (not/play)………aren't playing……badminton now.

9. He (learn)……is learning….…. English and I (read)……am reading…..…. a book now.

10. He often (have)……has.………coffee for breakfast.

11.What (be)……..is……the weather today? It (be)………is…….cold.

12. He usually (go jogging)………goes jogging……….….in the morning.

13. He often (go)………goes….……swimming. He (go)………íd going….…….swimming at the moment.

14. My sister (do)………does……..…aerobics every morning.

15.Lan (go)……………goes…..…….to school six days a week.

16. We (not/go)………don't go…..……..swimming in the winter.

17. He often (go)………goes……….the movie on Sunday.

18. The students (do)…………are doing..………..their homework now.

19. My mother ()………s…..…….iced tea.

20. He never (go)……goes….....camping because he (not/ have)……doesn't have………..…a tent.

We arrived back to Da Nang from an awesome long weekend with the girls in Nha Trang with an extra person. Our brother Quan had joined us on the return flight. He would stay in Da Nang with us for a week before heading home to An Lao to visit the family. This gave us an excuse to do a little sightseeing, as there were a number of sights he had not yet seen in Da Nang. When the siblings grew and became adults, they chose different cities to go off to school and work. Diem and her older brother Kevin came to Da Nang, the closest of the major cities to An Lao, and Quan, Hai, and Luan chose Saigon.

It gave us an opportunity to show Quan some things that I quite frankly hadn’t seen in awhile myself, and some places we frequent regularly. The rainy season was long in retreat, and it was now warm sunny days with the occasional evening shower. Da Nang is so incredibly beautiful in the spring. Not un Georgia. The first stop on the list was of course the Lady Buddha. The beautiful statue that looks down upon the beach and sea and brings luck to the local fisherman.

BUÔN MA THUỘT — I arrived in Buôn Ma Thuột, the capital of the Central Highlands province of Đắk Lắk and fondly referred to as the “Queen of Coffee”, after an eight-hour bus ride.

What really stuck with me after the trip was just how friendly and open the people were. Whether it was the motorbike taxi driver who enthusiasally spoke about his homeland and the interesting places I should visit, or the kind, loquacious hotel owner couple who shared their story and allowed me to stay past the checkout time.

Traffic jams were conspicuous by their absence, and locals were just pleasant to be around with.

“I think the people here are honest and natural compared to those in other cities," said Nguyễn Thị Ngọc Hân, a tourist from Hà Nội who was visiting Buôn Ma Thuột for the first time.

“Things here are not too commercial and have managed to retain their authenity.”

The second thing that struck me was the coffee, especially since I have been drinking coffee my whole life. The first time I took a sip of Buôn Ma Thuột coffee, its strong, bitter taste made me flinch. But then I found its aroma ening and its rich aftertaste lingering.

Its red basal soil makes Đắk Lắk an ideal place for growing coffee, and it accounts for a lion’s share of the country’s production.

Not surprisingly, coffee is a big part of the city’s culture and locals are proud of their high-quality brews. Everywhere I went I would see a coffee shop filled with people enjoying their morning cuppa before work.

A number of the city’s attractions are also linked to coffee.

"The city is living with the coffee,” Marian Takac, a Slovakia tourist, said.

“I can now see why it’s called the coffee capital of Việt Nam."

Buôn Ma Thuột is not all that interesting for tourists, was the locals’refrain, but I thought they were selling themselves short since there seemed to be so many interesting places to visit and things to do that one could easily spend a week there without feeling bored.

Trung Nguyên Coffee Village is a popular tourist attraction. It belongs to the Trung Nguyên Corporation and visitors can drink coffee in cafes with traditional Central Highlands architecture, take pictures of a miniature waterfall and see Central Highlands cultural artefacts.

Another attraction is the World Coffee Museum, which has numerous coffee-related artefacts from around the world: vintage coffee containers and cups, equipment and merchandise and traditional harvest tools of the Central Highlands.

Over the years many eco-tourism sites have emerged, such as KoTam Eco Tourism area. These offer visitors a chance to immerse themselves in the rich culture of the Central Highlands, see the greenery and waterfalls and lakes, wear traditional outfits, listen to traditional musical performances, and sample traditional foods and drinks roasted jungle fowl, cơm lam (sky rice grilled in bamboo shoots served with sesame) and rượu cần (fermented rice wine in earthen jugs, drank through long bamboo tubes).

Speaking of cuisine, bún đỏ (red rice noodles) is an absolute must-try. Mostly served in the afternoon and evening at street stalls around the city, the dish’s most unique characteris is the noodle, which is dyed a distinctive red colour from the broth made with grounded cashew.

Topped with crab roe, minced meat and fried onion, it is a tasty and filling dinner for around VNĐ30,000 (US$1.3).

To truly experience the traditional ethnic ambience of Buôn Ma Thuột, one must pay a visit to Buôn Akõ Dhông (Upstream village), which many locals think has been best able to maintain the area’s traditional roots.

A 20-minute motorbike ride from the city brings me to a place with a curious sight: modern houses situated next to traditional Central Highlands long houses, some turning their longhouses into restaurants and cafes.

One café I went into was filled with traditional local items such as gongs and jugs.

Majes natural beauty

"The city is fun but if you really want to experience the best that Buôn Ma Thuột has to offer, you have to check out Đray Nur and Đray Sap falls," a motorbike taxi drive told me.

Interested, I immediately booked a one-day tour to Đray Nur Waterfalls the next day.

After an hour’s bus drive we arrived at the fall. I still remember the feeling of excitement I had as we descended flights of rocky stairs amid the growing roar of the cascading water, and the moment the majes waterfall came into view was breathtaking.

It was a gigan stream of white rushing down, hitting rocks, splashing water everywhere, and creating a veil of mist.

There was also a crystal clear pond, reflecting the green of the layers of moss covering a nearby cliff.

Đray Nur Waterfalls, or "wife waterfall" in the language of the local Ê Đê ethnic group, is one of the most famous waterfalls in the Central Highlands.

Seeing other excited tourists, foreign and Vietnamese a, reacting in awe also added to the experience.

A mother of two remarked about the incredible view and size of the falls, saying how she really enjoyed getting closer to the falls than at any other place she had been to.

On our way back to the city, the bus stopped by some coffee bushes. They had bright, delicate flowers with a pleasant fragrance and our entire group was taken aback: no one had associated coffee with flowers.

After my week-long trip I took a flight back to HCM City. I felt a bit sad I had to leave quiet, peaceful Buôn Ma Thuột and return to chao HCM City.

Its people, culture and natural beauty left a strong impression on me.

^HT^

trả lời :

1. We always________ our exercises carefully.

A. do B. are doing C. does D. doing

2. I ____________ to school every day.

A. go B. goes C. going D. am going

3. My parents___________ in the garden now.

A. sitting B. are sitting C. is sit D. is sitting

4. Be quiet. The baby___________.

A. sleeping B. are sleeping C. is sleeping D. sleeps

5. It ___________ very cold now.

A. be B. are C. is D. am

6. Tom_____is travelling______ to the museums by bus now.

A. traveling B. are traveling C. is travel D. travels

7. The Bakers ______ dinner at the moment.

A. is having B. are having C. eating D. is eating

8. The United States _________ big.

A. had been B. are C. was D. is

9. Nam __________________ to Hue three times.

A. is B. was C. had been D. has been

10. Uncle Ho ___________ most of his life for our national Independence and freedom.

A. spent B. had spent C. was spending D. has spent

11. " Come back tomorrow. I ____________ it all to you.

A. have explained B. will explain C. was explaining D. explained

12. We __________________ each other since we left at school.

A. hadn't seen B. didn't see C. don't see D. haven't seen

13. She _________________ abroad many times.

A. has gone B. goes C. went D. had gone

14. He has _________________ in giving up smoking.

A. succeeds B. succeed C. succeeded D. succeeding

15. The train ______________ when we got to the station.

A. leaves B. will leave C. was already leaving D. had already left

16. One of the students in my class ________ absent today.

A. have been B. is C. were D. are

17. Ba s __________ TV every night.

A. watches B. watch C. watching D. is watching

18. Alex __________ married next month.

A. getting B. will get C. get D. Gets

19. I __________ that film two months ago.

A. see B. saw C. seeing D. will see

20. They both__________ from college in 1990.                              mk copppppppppppp okkkkkkkkk

A. had graduated B. graduate C. have graduated D. graduated

^HT^ 

Exercise 8: Choose the best option that best completes each sentence:

1. We always________ our exercises carefully.

A. do B. are doing C. does D. doing

2. I ____________ to school every day.

A. go B. goes C. going D. am going

3. My parents___________ in the garden now.

A. sitting B. are sitting C. is sit D. is sitting

4. Be quiet. The baby___________.

A. sleeping B. are sleeping C. is sleeping D. sleeps

5. It ___________ very cold now.

A. be B. are C. is D. am

6. Tom_____is travelling______ to the museums by bus now.

A. traveling B. are traveling C. is travel D. travels

7. The Bakers ______ dinner at the moment.

A. is having B. are having C. eating D. is eating

8. The United States _________ big.

A. had been B. are C. was D. is

9. Nam __________________ to Hue three times.

A. is B. was C. had been D. has been

10. Uncle Ho ___________ most of his life for our national Independence and freedom.

A. spent B. had spent C. was spending D. has spent

11. " Come back tomorrow. I ____________ it all to you.

A. have explained B. will explain C. was explaining D. explained

12. We __________________ each other since we left at school.

A. hadn't seen B. didn't see C. don't see D. haven't seen

13. She _________________ abroad many times.

A. has gone B. goes C. went D. had gone

14. He has _________________ in giving up smoking.

A. succeeds B. succeed C. succeeded D. succeeding

15. The train ______________ when we got to the station.

A. leaves B. will leave C. was already leaving D. had already left

16. One of the students in my class ________ absent today.

A. have been B. is C. were D. are

17. Ba s __________ TV every night.

A. watches B. watch C. watching D. is watching

18. Alex __________ married next month.

A. getting B. will get C. get D. Gets

19. I __________ that film two months ago.

A. see B. saw C. seeing D. will see

20. They both__________ from college in 1990.

A. had graduated B. graduate C. have graduated D. graduated

~ Hok tốt nehs ~