Country life gives him peace and quiet which is he can't enjoy while living in big citi

问题补充：

Country life gives him peace and quiet, which is he can enjoy while living in big cities.

A. that

B. why

C. where

D. what

答案：

A. that

B. why

C. where

(答案→)D. what

解析：D 考察连接词。What he can’t enjoy是表语从句，what在表语从句中做动词enjoy的宾语。