For which of the following reasons can natural pollutants play an important role in controlling air pollution?

Câu hỏi :

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 following questions from 55 to 64.

A. They function as part of a purification process. 

B. They occur in greater quantities than other pollutants. 

C. They are less harmful to living beings than other pollutants 

D. They have existed since the Earth developed

* Đáp án

* Hướng dẫn giải

Đáp án : A

 “Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides, are found in nature”

“These serve as an air purification scheme…” : những cái này đóng vai trò như 1 quy trình làm sạch => A

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