试题题干
Translate the following sentence into Chinese.
Once we thought of pollution as meaning simply smog—the choking, stinging, dirty air that hovers over cities.
参考答案
试题解析
考点：smog (n.) 烟雾 ；simply 仅仅；hover (v.) 盘旋，翱翔 。
句子结构：句子主干为we thought of pollution as meaning simply smog，破折号后进一步说明smog的含义。