is known to us all is that the Olympic Games will take place in Beijing.A. ItB. What

问题补充：

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

A. It

B. What

C. As

D. Which

答案：

A. It

(答案→)B. What

C. As

D. Which

解析：考查名词性从句的用法。根据句子分析，第二个is 前面的 is known to us all为主语从句，句中缺少主语，根据句意分析，应该选择能充当成分的What。