Even the top students in our class can't work out this problem, so it ___bevery difficult.
A. may
B. must
C. can
D. need
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The children___ play football on the road.
A. can't
B. can
C. mustn't
D. must
-Must I do my homework at once? -No, you___.
A. needn't
B. mustn't
C. can't
D. may not
You had better stay here, ___ you?
A. didn’t
B. don’t
C. hadn’t
D. aren’t
You'd better ___ late next time.
A. not to be
B. not be
C. won't be
D. don't be
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