31.It may someday be worthwhile to try to recover uranium from seawater, but at present this process is prohibitively expensive.

(A) It may someday be worthwhile to try to recover uranium from seawater

(B) Someday, it may be worthwhile to try and recover uranium from seawater

(C) Trying to recover uranium out of seawater may someday be worthwhile C

(D) To try for the recovery of uranium out of seawater may someday be worthwhile

(E) Recovering uranium from seawater may be worthwhile to try to do someday

Key: A
那位分析一下，why B,C are wrong?

个人看法：
选项B：try and recover uranium from seawater，是try和 recover uranium from seawater（有一天尝试//和//从水中获得uranium是值得的）并列呢，还是try和 recover （有一天尝试uranium从水中并获得uranium从水中）并列？？但是无论怎么并列，意思上都讲不通不如A意思上好.

选项C：out of 不如from意思上好，且recorver f且这个表达主语过长，不如使用形式主语好.