Is "The man which I met yesterday is a doctor" correct?

Why

Divyansh's word choice, "which", genuinely does the same connecting JOB as "who" — both link extra information back to a noun mentioned earlier in the sentence. English splits this connecting word based on WHAT kind of noun it's pointing back to, though: "who" is reserved for people, while "which" is reserved for things, animals, and objects. "The man" is a person, so the sentence needs "who" to point back to him correctly; "which" would sound as if a person were being talked about the way an object is. Test: notice you'd never say "the chair who I sat on" — that sounds equally wrong in the opposite direction, confirming this is a genuine people-versus-things split, not a random preference. His sister is right: "who" is used for people and "which" for things, so it should be "the man WHO I met", not "which".