is known to us all is that the Olympic Games will take place in London.A. AsB. WhatC

问题补充：

is known to us all is that the Olympic Games will take place in London.

A. As

B. What

C. That

D. It

答案：

A. As

(答案→)B. What

C. That

D. It

解析：考查主语从句的连接词。此处what is known to us all是主语从句。