In a Market System, How Are the Terms of Exchange

In a market system, how are the terms of exchange established?

A) Consumer advocacy groups establish fair prices for items, and most firms follow these pricing guidelines because they don't want to anger their consumers.
B) Industry associations establish an acceptable price range for each commodity sold within the industry, and member firms are obligated to abide by association guidelines.
C) The forces underlying supply and demand interact to determine a market price.
D) Federal legislation establishes maximum prices for most goods, and state governments regulate the prices of any remaining items.