All possible means to save the wounded soldier.
A. has been tried
B. have been tried
C. is to be tried
D. are trying
网友回答
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。