Question

if you had told us earlier _he was, we could have

if you had told us earlier _he was, we could have introduced him at the meeting. 为什么用who,而不是whom？空白处不是后面was的宾语吗？

Answer 1

who,whom在从句中分别作主语和宾语,指人,其中 who可以替换whom,但是介词后面一定要用whom,whom是who的宾格形式,用作疑问代词 .
例I want to know whom/who you are waiting for?
I want to know for whom you are waiting?
Mrs Read is the person to whom you should write．