Question

[Lê Quỳnh Anh]

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.

It’s a sound you will probably never hear, a sickened tree sending out a distress signal. But a group of scientists has heard the cries, and they think some insects also hear the trees and are drawn to them like vulture to a dying animal. Researchers with the US Department of

Agriculture’s Forest Service fastened sensors to the bark of drought-stricken trees clearly heard distress calls. According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50-kilohertz range. (The unaided human ear can detect no more than 20 kilohertz). Red oak, maple, white pine, and birch all make slightly different sounds in the form of vibrations at the surface of the wood.

The scientists think that the vibrations are created when the water columns inside tubes that run along the length of the tree break, a result of too little water following through them. These fractured columns send out distinctive vibration pattems. Because some insects communicate at ultrasonic frequencies, they may pick up the trees' vibration and attack the weakened trees. Researchers are now running tests with potted trees that have been deprived of water to see if the sound is what attracts the insects. “Water-stressed trees also smell differently from other trees, and they experience thermal changes, so insects could be responding to something other than sound”, one scientist said.

It can be inferred from the passage that the sounds produced by the trees ________ .

A. are the same no matter what type of tree produces them

B. cannot be heard by the unaided human ear

C. fall into the 1-20 kilohertz

D. serve as a form of communication among trees

Answer 1

[Dương Hoàn Anh]

Đáp án B

Có thể suy ra từ đoạn văn rằng các âm thanh được tạo ra bởi cây ________.

A. tương tự cho dù là loại cây tạo ra chúng

B. không thể nghe thấy bằng tai người mà không có thiết bị trợ giúp.

C. rơi vào khoảng 1-20 kilohertz

D. làm việc như một hình thức giao tiếp giữa các cây

Thông tin ở câu: “According to one of the scientists, most parched trees transmit their plight in the 50-hertz to 50-kilohertz range. (The unaided human ear can detect no more than 20 kilohertz)” (Theo một trong các nhà khoa học, hầu hết các cây khô héo truyền tải tình trạng của chúng trong khoảng 50-hertz tới 50 kilohertz. (Tai người mà không có thiết bị trợ giúp chỉ có thể phát hiện âm thanh không quá 20 kilohertz.))