.请说明原因...I want them to know that what they did for me was not___.A.in vain B.for vain 我查词典 这两个词都一样的意思...该选什么?

.请说明原因...I want them to know that what they did for me was not___.A.in vain B.for vain 我查词典 这两个词都一样的意思...该选什么?
.请说明原因...
I want them to know that what they did for me was not___.
A.in vain B.for vain
我查词典 这两个词都一样的意思...该选什么?

.请说明原因...I want them to know that what they did for me was not___.A.in vain B.for vain 我查词典 这两个词都一样的意思...该选什么?
A
没有看到B的用法
好像没有for vain这个用法,只有in vain,表示徒劳

A

A
固定用法 没什么好说的
意思是徒劳的