All possible meansto save the wounded soldier.A. has been triedB. have been triedC. is to

问题补充：

All possible meansto save the wounded soldier.

A. has been tried

B. have been tried

C. is to be tried

D. are trying

答案：

A. has been tried

(答案→)B. have been tried

C. is to be tried

D. are trying

解析：means是单复数同形名词，谓语的单复数取决于句子意思，如all/those/a lot of means动词用复数；every/this/that means动词用单数。