So many natural disasters are believedover the recent years because of the frequent unreas

问题补充：

So many natural disasters are believedover the recent years because of the frequent unreasonable mankind activities.

A. to have come about

B. to come about

C. coming about

D. to be coming about

答案：

(答案→)A. to have come about

B. to come about

C. coming about

D. to be coming about

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