He'll never forget the days______ he lived in the countryside, which is a great help to his writing.
A.that
B.when
C.which
D.where

A.A.that
B.when
C.which

【参考答案】

B
解析：此题中的which引导非限定性定语从句，此类从句中的关系代词不能出现that，更不能出现what。