Answer:
interrogative/nominative
Explanation:
Who is an interrogative/nominative pronoun. It's interrogative because it is used to form the question "who told you this?" To remember think interrogation. An interrogation is when someone asks many questions to get at the truth. Nominative is when the subject is renamed. Here since we don't know "Who", who is the subject so it is in nominative form. Objective form receives the action. "You" is written in objective form.
