The Gasoline Market in the United States Is Often Said

The gasoline market in the United States is often said to be highly competitive.But it is not perfectly competitive.What makes this market not perfectly competitive?

A) If you don't like the price at one gas station, you can go to another one.
B) Different companies put different additives (designed to reduce engine deposits) in the gas they sell.
C) An individual seller can dictate what price a consumer pays for its gas.
D) Gas stations located near each other tend to charge the same or very similar prices.