It: It was him who she had mentioned before she died

[Tung Quoc]

Dear teachers,

Please choose the correct sentences:

1. It was him who she had mentioned before she died.
2. It was him that she had mentioned before she died.
3.It was him she had mentioned before she died.

Is there a rule?
I think all are correct. How about you?
Quoc

[Alan]

Hi,

I have a question for you. Where did you find these sentences?

Alan
_________________
English as a Second Language
You can read my ESL story New year resolutions

[Tung Quoc]

All are correct in grammar?

These are from my teacher.