फ़्लैशकार्ड

Who serves as a grammatical subject, representing the person who performs an action or about whom a statement is made. Whom serves as a grammatical object, representing the person who receives an action from a verb or follows a preposition like to, with, or for. Everyday spoken English frequently uses who in both subject and object positions, while formal written English reserves whom for objects.

Who unlocked the meeting room before our morning discussion?