問題詳情

17. What prevents toxic fumes from rising into the upper atmosphere?
(A) Smoke from factories.
(B) Polluted air from vehicles.
(C) Pollution levels in a city.
(D) Moisture in the air.

參考答案

答案:D
難度:非常困難0
統計:A(2),B(1),C(0),D(0),E(0)

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