—Where is Bob? I cannot find him anywhere.—He       have been off long. I heard him make a call just now.
#90189
A
shouldn’t
B
can’t
C
mustn’t
D
needn’t
推荐题目
 It is required in our school that lights in students’ rooms ______ off by 11o’clock.
#87254
A
be switched
B
would switch
C
should switch
D
must be switched
It is required that no smoking ______ in the school.
#89784
A
was allowed
B
be allowed
C
would be allowed
D
had been allowed
Are you still here? You ______ home hours ago. 
#89553
A
should go
B
should have gone
C
might go
D
may have gone
. — Please don’t make a noise.— _____. I’ll be as quiet as a mouse.
#90207
A
Yes, I won’t
B
No, I won’t
C
No, I will
D
Yes, I will