Question

【题目】At present there are more and more private cars. They have caused serious air________ (pollute).

Answer 1

【答案】pollution

【解析】

句意：目前有越来越多的私家车。它们造成了严重的空气污染。

pollute动词，污染。结合句意和空前air可知这里用短语“空气污染”air pollution，所以这里用pollute的名词形式pollution，故填pollution。