Question

【题目】_________ that causes heavy haze sweeping over china remains unknown to many scientists.

A. what it is B. what is it

C. who is it D. who it is

Answer 1

【答案】A

【解析】

试题分析：考察强调句。该句是强调句的疑问句，陈述句应该是it is … that cause heavy haze。又因为原因并没有查明是人还是物，所以疑问词用what。该句意思为：是什么导致了席卷中国的雾霾对于很多科学家来说还是未知的。