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

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：考察从句连词选择，根据句子结构可知，该句为主语从句，作第二个is的主语，主语从句中缺少主语，所以选择what，it是形式主语，as引导的定语从句，可以作主语，which用于有选择范围的主语。