he is always studying hard is well known us all.A. How toB. What toC. That toD. Wheth

问题补充：

he is always studying hard is well known us all.

A. How, to

B. What, to

C. That, to

D. Whether, by

答案：

A. How, to

B. What, to

(答案→)C. That, to

D. Whether, by

解析：考查主语从句和固定短语。本题第一空的that引导的是主语从句That he is always studying hard, that在句中不充当任何成分，只起引导和连接的作用。第二空是没有固定词组be known to sb为sb所知；句意：他总是认真学习这件事情是我们众所周知的。故C正确。