it is me/I
 

It is/was men. + relative clause
When a relative clause comes after an expression like It is/ was me/I, there are two possibilities:
object form + that (very informal)
It's me that needs your help.
It was him that told the police.
subject form + who (very formal)
It is I who need your help.
It was he who told the police.
We can avoid being too formal or too informal by using a different structure.
He was the person/the one who told the police.

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