Tell me the reason you are late.A. thatB. whyC. whichD. where

问题补充：

Tell me the reason you are late.

A. that

B. why

C. which

D. where

答案：

A. that

(答案→)B. why

C. which

D. where

解析：考查定语从句。本定语从句的先行词是the reason,后面定语从句的结构很完整，故使用关系副词，当先行词是reason的时候，关系副词用why。故B正确。