You worry about their safety．They are old enough to take care of themselves.A. mustn’t B.

问题补充：

You worry about their safety．They are old enough to take care of themselves.

A. mustn’t

B. needn’t

C. can’t

D. wouldn’t

答案：

A. mustn’t

(答案→)B. needn’t

C. can’t

D. wouldn’t

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