Most Supermarkets Charge the Same Price for the Majority of Goods

Most supermarkets charge the same price for the majority of goods sold.This suggest that

A) the government regulates prices of most products sold in supermarkets.
B) supermarkets have colluded to fix prices on most of the goods sold.
C) mark-ups reflect the degree of competition in the supermarket industry.
D) the large supermarket chains are price leaders and smaller grocers take these prices as given.