Youbuy a gift but you can if you want to.A. mustB. mustn'tC. have toD. don't have to

问题补充：

Youbuy a gift, but you can if you want to.

A. must

B. mustn

C. have to

D. don have to

答案：

A. must

B. mustn

C. have to

(答案→)D. don have to

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