is known to us all is that the old worker for life was hard in the past still works hard

问题补充：

is known to us all is that the old worker，for life was hard in the past，still works hard in his seventies.

A. As；whom

B. What；whose

C. It；whose

D. What；whom

答案：

A. As；whom

B. What；whose

C. It；whose

D. What；whom

解析：D

解析考查名词性从句和定语从句的引导词。第一个空中what引导一个主语从句，并作从句的主语。第二个空代替先行词the old worker，并作介词for的宾语，用whom。