Answer:
a. vehicle color
Step-by-step explanation:
One might expect that the cost of owning a vehicle would not be a function of its color. There is no reason to believe that a blue car gets better gas mileage than a green car of the same make, model, and equipment. So, the appropriate choice is ...
a. vehicle color
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However, vehicle color may play a role in ownership costs if more money is spent on washing a white car than would be spent on a black or beige car. Similarly, a light-colored car may require less use of an air-conditioner in the summer sun than does a dark-colored car, ultimately affecting fuel cost. It isn't always obvious what the features of a vehicle are that contribute to ownership cost.