is known to us all is that we should do as much as we can stop the pollution of the envir

问题补充：

is known to us all is that we should do as much as we can stop the pollution of the environment.

A. It; help

B. What; to help

C. As ; to help

D. That ; help

答案：

A. It; help

(答案→)B. What; to help

C. As ; to help

D. That ; help

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