The amounts of oxygen and nitrogen in the air almost always

Câu hỏi :

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.

A. The amount of

B. almost always

C. stable

D. vary

* Đáp án

D

* Hướng dẫn giải

Đáp án D

- The amount of + N + V chia số ít: số lượng …

ð Đáp án D (vary => varies)

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