I'll never forget the day I was bornA. whenB. that C. on whichD. both A and C

问题补充：

Ill never forget the day I was born．

A. when

B. that

C. on which

D. both A and C

答案：

A. when

B. that

C. on which

(答案→)D. both A and C

解析：考查定语从句。本定语从句的先行词是the day,定语从句的结构很完整，主语是I，后面是系表结构，句子很完整，故使用关系副词，先行词指时间，故使用关系副词when, 关系副词经常等于介词+关系代词。本题when=on which.故D正确。