is well known that great changes have taken place in China recently.A. ThatB. AsC. WhichD.

问题补充：

is well known that great changes have taken place in China recently.

A. That

B. As

C. Which

D. It

答案：

A. That

B. As

C. Which

(答案→)D. It

解析：考查It 作形式主语，真正的主语是that 后的从句，句意：人们都知道最近在中国发生了巨大变化。所以选D。