Câu hỏi :

The word "these" in paragraph 2 refers to

A. chemical substances

B. industrial activities

C. our daily lives

D. excessive burning of fuel for cooking, driving

* Đáp án

A

* Hướng dẫn giải

Dẫn chứng: .... releases a huge amount of chemical substances in the air every day; these pollute the air. 

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