is known to us all is that America is a developed country the First World.A. Which; belo

问题补充：

is known to us all is that America is a developed country the First World.

A. Which; belonging to

B. as; belonging to

C. what; belonging to

D. It; belonging to

答案：

A. Which; belonging to

B. as; belonging to

(答案→)C. what; belonging to

D. It; belonging to

解析：我们都知道美国是属于第一世界的发达国家。第一空是主语从句；第二空是现在分词短语作定语。