Studies show that trees and plants improve air ______________ which is very bad now because of the traffic.

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.

Studies show that trees and plants improve air ______________ which is very bad now because of the traffic.

A. quality

B. atmosphere
C. quantity 
D. amount

Trả lời

Chọn A

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