—She was late for the party.
—That’s she had forgotten the exact time.
A. why
B. how
C. because
D. whether
网友回答
A. why
B. how
(答案→)C. because
D. whether
解析：考查表语从句：句意：--她聚会迟到了。--这是因为她忘了确切的时间。That is because…那就是因为…，because引导的是表语从句，that is why…那就是…的原因， how怎样，whether是否，不符合句意，选C。