Question

________ is known to us all is that London will host the 30th Olympic Games next summer.

A. As    B. Which

C. It    D. What

Answer

D

【解析】考查主语从句。as is known to us意为“众所周知”，是as引导的非限制性定语从句，必须要用逗号与后面的句子隔开，本句没有，故排除A项；B项表示“哪一项”，与语境不符，排除；C项如果用It的话，it是做形式主语，句型结构是It is known to us all that，但根据all后面还有is判断排除C项；分析句子，空处缺少的是主语从句的引导词，引导词作主句的主语，表示“……的事情”可知，故用what引导主语从句。故选D。

【名师点睛】

１. As everyone knows众所周知。／As is known to us众所周知。它们是as引导的非限制性定语从句，as指后面的整个句子，并一定要用逗号与后面的句子隔开。如：As is known to us, the Great Wall is in China.

2. What is known to all is that…众所周知的是……。此句是what引导的主语从句，what起双重作用。如：What is known to all is that the Great Wall is in China.

3. It is known to us all that…，这里it作形式主语，that引导的从句为真正的主语。如：It is known to us all that he is a man everybody believes in.