题干
—You look so tired. What's the matter?
—I was so busy that I didn't go to bed 12 o'clock last night.
A：until
B：unless
C：if
D：so
答案(点此获取答案解析）
A
—You look so tired. What's the matter?
—I was so busy that I didn't go to bed 12 o'clock last night.
A：until
B：unless
C：if
D：so
