Every possible means__,but theproblem remains unsolved.A.has been triedB.have been triedC.has triedD.have triedA?

问题描述:

Every possible means__,but theproblem remains unsolved.
A.has been tried
B.have been tried
C.has tried
D.have tried
A?

对的,选A means这里是方式的意思,单数来的

A
已经被尝试过了