is known to us all is that the Olympic Games will take place in Rio de Janeiro.A. I

问题补充：

is known to us all is that the Olympic Games will take place in Rio de Janeiro.

A. It

B. What

CAs

D. Which

答案：

A. It

(答案→)B. What

C. As

D. Which

解析：考查名词性从句。本题考查what引导的主语从句，从句中缺少主语，故用关系词what引导。句意：众所周知，奥运会将在里约热内卢举办。故B正确。