The puzzle assumes that if someone rents a vehicle, then it must be a car. But we can in no way make that assumption.
Agreed that most often, rented vehicles are cars, but that is not good enough mathematically to say that it must be a car and nothing else.
People have been known to rent planes not very infrequently, and all of the 4 types of vehicles can be rented.Secondly, it is not much of a puzzle if it has 3 answers. It is just like saying that if there were no restrictions, then it would have 24 answers. It is too childish.
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