Commentator: For a free market to function properly, each prospective buyer of an item must be able to contact a large number of independent prospective sellers and compare the prices charged for the item to what the item is worth. Thus, despite advertised prices and written estimates available from many of its individual businesses, the auto repair industry does not constitute a properly functioning free market. The conclusion of the commentator's argument follows logically if which one of the following is assumed?
A: People do not usually shop for auto repairs but instead take their autos to their regular repair shop out of habit.
B: Because it is not regulated, the auto repair industry does not have standardized prices.
C: Many auto repair shops charge more for auto repairs than these repairs are worth.
D: Some persons who are shopping for auto repairs cannot determine what these repairs are worth.
Choose A, B, C or D as your solution.
D