问题补充:
The boss believed Toms reason for being late for work is he had to help his grandma cook.
A. why
B. that
C. where
D. because he
答案:
A. why
(答案→)B. that
C. where
D. because he
解析:考查表语从句。That he had to help his grandma cook是一个表语从句,这个句中结构很完整,that只起引导作用,不充当任何成分。