Should you use whom you trust or who you trust?

Answer 1

You can use both who and whom you trust.

Who can be used as a subject and an object of a clause, but not object of a preposition.

Whom can only be used as an object.

She is the one who is always there for me. (not whom because who is the subject of is)

_She is the only one who (_or whom) I trust. (object of trust)

She is the one on whom (not who) I can rely . (object of the preposition on)

Answer 2

You would use whom not who.