is known to us all that the Olympic Games will take place in LondonA. ItB. WhichC.

问题补充：

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

A. It

B. Which

C. As

D. What

答案：

(答案→)A. It

B. Which

C. As

D. What

解析：考查主语从句。句中it作形式主语，真正的主语为that the Olympic Games will take place in London。