31．Children above 12 are able to take part in skiing or other activitiesfor them.A. having

问题补充：

31．Children above 12 are able to take part in skiing or other activitiesfor them.

A. having designed

B. designing

C. to design

D. Designed

答案：

A. having designed

B. designing

C. to design

(答案→)D. Designed

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