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

问题补充：

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

A. It

B. Which

C. As

D. What.

答案：

A. It

B. Which

C. As

(答案→)D. What.

解析：考查主语从句：分析句子成分可知第二个is是主句的谓语，前面都是主语从句，而主语从句缺少主语，填what，句意是：我们都知道的是奥运会将在伦敦举行。选D。