How is the form of who or whom used in the sentence? we're trying to find out whose car is parked in front of our driveway? subject direct object object of a preposition possessive

I think that "whose" is the possessive form of who and in this case it is an adjective that explains the "car" ownership and in this case the speaker may want to find out who owns the car so they can be contacted to move it away from their driveway so they can get out, for example.

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