Who (subject) vs. Whom (object) vs. Who (modifier) Who called whom

?id? First, lets define subject pronouns and object pronouns.Subject pronouns are the actors of the sentence: I, you, he, she, we and they are common subject pronouns.Object pronouns are the receivers of the action. Me, you, him, her, us and them are common object pronouns. "Who is a also a subject pronoun, so use who in places where you would say he or she: Who wants to know?Who is it? (which explains why it is he is the correct usage, not it is him)Who is your favorite writer?" Conversely, "whom is an object pronoun. Use whom in places where you would say him or her:To whom are you speaking? (I am speaking to her.)To whom was this letter sent? (It was sent to him.)However, who can also serve as a modifier (a word used to describe someone further), which can create some confusion among those who understand the correct usage of whom in all other instances.The rule is easy: whom should never be used as an adjectival modifier, no matter whether it refers to the subject or the object of a s entence. In other words, if the word is used to describe someone already mentioned, then you should always say "who", not "whom". I am looking for a tutor whom understands every in and out of the GMAT verbal = incorrectI am looking for a tutor who understands every in and out of the GMAT verbal = correctWhy? Because the object of these sentences is the word tutor, not the word who. In this case, who serves as more of an adjectival modifier to the main object. Here is the POS (part of speech) template: noun + whom = incorrect preposition + whom = correct-Brian