Question

【题目】________is known to us is that tobacco contains nicotine and other harmful products，so you should give up smoking.

A．As B．It

C．What D．Which

Answer 1

【答案】C。

【解析】考查主语从句。句意：我们知道烟中含有尼古丁和其他有害成分，因此你应该戒烟。________is known to us这一部分在句中作主语，是一个主语从句，主语从句中动词know缺少宾语，故用what引导。