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Câu hỏi:

21/07/2024 290

plant species that are well adapted to survival in dry climates are being looked at for an answer in developing more efficient crops to grow on marginally arable lands.

Plants use several mechanisms to ensure their survival in desert environments. Some involve purely mechanical and physical adaptations, such as the shape of the plant's surface, smaller leaf size, and extensive root systems. Some of the adaptations are related to chemical mechanisms. Many plants, such as cacti, have internal gums and mucilage which give them water-retaining properties. Another chemical mechanism is that of the epicuticular wax layer. This wax layer acts as an impervious cover to protect the plant. It prevents excessive loss of internal moisture. It also protects the plant from external aggression, which can come from inorganic agents such as gases, or organic agents which include bacteria and plant pests.

Researchers have proposed that synthetic waxes with similar protective abilities could be prepared based on knowledge of desert plants. If successfully developed, such a compound could be used to greatly increase a plant's ability to maintain health in such adverse situations as inadequate water supply, limited fertilizer availability, attack by pests, and poor storage after harvesting

The word “It” in the 2nd paragraph refers to________

A. the epicuticular wax layer

Đáp án chính xác

B. the loss of internal moisture

C. an impervious plant like cover

D. another chemical mechanism

 Xem lời giải

Trả lời:

verified Giải bởi Vietjack

Đáp án A
Như câu 49 => it là the epicuticular wax

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CÂU HỎI HOT CÙNG CHỦ ĐỀ

Câu 1:

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.

       Revising for exams is not as easy as it looks. You will need to work out which routine suits you best, and then stick to it. Some people like studying at night when it’s quiet, whereas others find the early morning is a good time to get things done. You might enjoy ___ (1) ____ to music while you revise, but this can be ___ (2) ___. Can you really concentrate ___ (3) ____ two things at once? So think ___ (4) ____ you turn your radio on.

       Your ___ (5) ____ is also important while you are revising. This may be a more than usually ___ (6) ____ period of your life, when you should take extra care to eat properly. No missed meals, or junk food, or ___ (7) ____ cups of coffee! Get plenty of exercise as well. If you have got fed up with ___ (8) ____ you’re doing, or find it hard to concentrate, go for a walk to clear your head. ___ (9) ____ exercise will help to keep your body fit and your brain working ___ (10) ____.

       Finally, you also need to take time off. Go out occasionally, see your friends, make time to relax. Then you will return to your studies fresh and full of enthusiasm.Question 10

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Câu 2:

Her mother, ______ has been working for thirty years, is retiring next month

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Câu 3:

She was _____ she could not say anything

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Câu 4:

No sooner ______ into the bath than someone knocked at the door

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Câu 5:

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions

Bella had better (A) to change her study habits if she (B) wants to be admitted (C) to (D) a good college

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Câu 6:

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions

You (A) should stop  (B) to smoke because it is very harmful (C) to  (D) your health

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Câu 7:

Mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that is CLOSEST in meaning to the underlined part in each of the following questions

Let's wait here for her; I'm sure she'll turn up before long

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Câu 8:

I am late because my alarm clock never ______ this morning

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Câu 9:

We have had the roof of our house ______

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Câu 10:

Of two new teachers, one is experienced and _________

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Câu 11:

I’d rather he ______ the door blue

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Câu 12:

In the hotel lobby, the detective caught ______ of the man whom he had been hired to follow

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Câu 13:

By the end of next week, you ______ your assignments

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Câu 14:

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.

       Revising for exams is not as easy as it looks. You will need to work out which routine suits you best, and then stick to it. Some people like studying at night when it’s quiet, whereas others find the early morning is a good time to get things done. You might enjoy ___ (1) ____ to music while you revise, but this can be ___ (2) ___. Can you really concentrate ___ (3) ____ two things at once? So think ___ (4) ____ you turn your radio on.

       Your ___ (5) ____ is also important while you are revising. This may be a more than usually ___ (6) ____ period of your life, when you should take extra care to eat properly. No missed meals, or junk food, or ___ (7) ____ cups of coffee! Get plenty of exercise as well. If you have got fed up with ___ (8) ____ you’re doing, or find it hard to concentrate, go for a walk to clear your head. ___ (9) ____ exercise will help to keep your body fit and your brain working ___ (10) ____.

       Finally, you also need to take time off. Go out occasionally, see your friends, make time to relax. Then you will return to your studies fresh and full of enthusiasm.Question 6

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Câu 15:

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.

       Revising for exams is not as easy as it looks. You will need to work out which routine suits you best, and then stick to it. Some people like studying at night when it’s quiet, whereas others find the early morning is a good time to get things done. You might enjoy ___ (1) ____ to music while you revise, but this can be ___ (2) ___. Can you really concentrate ___ (3) ____ two things at once? So think ___ (4) ____ you turn your radio on.

       Your ___ (5) ____ is also important while you are revising. This may be a more than usually ___ (6) ____ period of your life, when you should take extra care to eat properly. No missed meals, or junk food, or ___ (7) ____ cups of coffee! Get plenty of exercise as well. If you have got fed up with ___ (8) ____ you’re doing, or find it hard to concentrate, go for a walk to clear your head. ___ (9) ____ exercise will help to keep your body fit and your brain working ___ (10) ____.

       Finally, you also need to take time off. Go out occasionally, see your friends, make time to relax. Then you will return to your studies fresh and full of enthusiasm.Question 2

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