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

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

(答案→)D. What; whom

解析：句意：我们都知道的是对他来说过去的生活很难的那个老工人70几岁了还在辛苦的工作。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。如果填whose，定语从句就没有主语了。选D。