The pollution problem here seems to get more and more serious .Something with it .A. has d

问题补充：

The pollution problem here seems to get more and more serious .Something with it .

A. has done

B. must be done

C. is doing

D. was done

答案：

A. has done

(答案→)B. must be done

C. is doing

D. was done

解析：此题重点考查含有情态动词的被动语态的基本构成和用法。