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

Câu hỏi :

Read the following passage and choose the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions from 33 to 42.    

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 are other pollutants. 

D. They have existed since the Earth developed.

* Đáp án

A

* Hướng dẫn giải

Chọn A

Dòng 4 đoạn 2 “These serve as an air purification scheme”: chúng phục vụ như 1 kết hợp làm sạch-> quá trình làm sạch.

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