That is the day I'll never forget.A. whichB. on whichC. in whichD. when

问题补充：

That is the day Ill never forget.

A. which

B. on which

C. in which

D. when

答案：

A. which

B. on which

C. in which

D. when

解析：which是关系代词，在从句中作forget的宾语。其他几个答案都不能作宾语。