问题

Jack _______ swim when he was five years old.
A:can
B:could
C:may
D:must
B:could
C:may
D:must
正确答案是:
同类题型
____________ people went to the concert which was held in People’s Square the night of May Day.
Could you tell me _______ it take to go from here to Harbin by car?—About fifty minutes.
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