问题补充:
is known to us is that the Olympic Games will be held in Rio de Janeiro, Brazil.
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,分析句子可以发现,第二个is是这句话的谓语,前面的is指主语从句的谓语,that引导的是表语从句,在主语从句中is前面缺少主语,用what连接主语从句,句意:我们都知道的事情是,奥运会在里约热内卢举办。选D。