题目内容：

He must be at home,__the light in his room is on.
A because
B as
C because of
D for
He felt tired,__he kept on working.
A and
B or
C but
D for

优质解答

He must be at home,__the light in his room is on.A because B asC because ofD for选A,为什么?因为“He must be at home”指已经不能改了,“_the light in his room is on”表原因,而表示“因为”的,在以上选择中...