题目内容：

The reason ___he gave for being late was ____he forgot to use the alarm clock
A which ,because
B why ,because
C which ,that
D that because
,为什么

优质解答

which引导定语从句,在定语从句中代替先行词reason在定语从句中作gave的宾语；that 在此引导表语从句,在表语从句不充当成份,也没有实际意,且一般不可省略.
句意：他给的迟到的理由是他忘了定闹钟.