I can't remember __(who/whom) it was.

Question

I can't remember __(who/whom) it was. 为什么答案填who？ who在从句中作什么成分？谢谢！！
谢谢回答。。who在从句中到底是做主语还是表语？假如作表语也是用主格吗？假如单独看一个正常语序的疑问句，比如【who is she？】这句里面的who是不是做主语？在题目中的who it was宾语从句里，who是做主语还是表语？
不好意思还有几题。。
2.No onw but (she/her) ever made a perfect score on the test. 答案是her
3. Was it (she/her) you were talking about? 答案是she
4. It is I who (is, am) the only friend you've got. 答案是am
麻烦都解释一下，万分感谢！！！

Answer 1

whom 做及物动词的宾语或是介词的宾语
who it was宾语从句里，who是做表语
特殊疑问句中顺序应该是Who was it?

who is she? She is Lucy. 显然who是做表语

but 介词,后面用宾格
you were talking about 定语从句修饰前面的she,she在这里应该是强调
强调句型 It is + 被强调部分 + that(who)...,原句应该是I am the only friend you've got.强调主语I

Answer 2

who it was 作为整个句子的宾语从句，who是从句中的主语

Answer 3

who引导宾语从句，在从句中做表语，不是宾语。whom引导应该是在从句中做宾语。