Use nominative pronouns
(I, we, you, he, she, they, and who) to complete the meaning
of being verbs (is, am, was, were, be, been, are).
This is he. The project chairmen are they. The accountant who made the mistake is she. Who did you say that man is? (In this
sentence, the being verb comes at the end of the sentence,
but it is still completed by the pronoun who.)