Traditional grammarians think a linking verb, such as the verb to be, must be followed by the subjective form (I, he, she, we, they).
Based on that traditional rule, it is correct to say:
It is I.
It is we.
Having told you the traditional rule, common usage has long endorsed the objective form (me, her, him, us, them).
It is me.
It is us.
Does that make it OK? I think so, unless you want to be very formal.
However, when we add a ‘who’ clause many people still use the subjective form.
It is I who raised the question.
It is me who raised the question.
Which usage do you prefer?
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