---Look at the boy running on the playground. Is it David? ---It ______ be him. I saw him go to the teachers’ office just now.
#76689
A
mustn’t
B
can’t
C
couldn’t
D
must
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As it turned out to be the most important meeting in the year, you ____ so casually. 
#62823
A
Shouldn’t dress up
B
shouldn’t have dressed up
C
needn't have dressed up
D
couldn’t dress up