Anewly made car will have a model number, a parts number, and a serial number. a model number is assigned by the manufacturer to identify each type of car. a parts number identifies one part of the smaller parts that make up the car. a serial number is unique to each car produced and identifies it. which relation is a function? . a> (parts number, serial number). b> (model number, parts number). c> (serial number, model number). d> (serial number, part number).