Not easy as the problem of pollution is no one should just stop trying.A. to solveB. to b

问题补充：

Not easy as the problem of pollution is, no one should just stop trying.

A. to solve

B. to be solve

C. solving

D. being solved

答案：

(答案→)A. to solve

B. to be solve

C. solving

D. being solved

解析：考查固定结构。Not easy as the problem of pollution is,是as引导的让步状语从句，是一个倒装句，正常语序应是as the problem of pollution is not easy结构，考查做某事不容易结构，即be not easy to do 结构，所以选A。