Which of these is a calculation that determines the difference in revenue of a retailer's existing supplies over a certain period of time,usually quarterly,compared to the identical period of time,in a prior year?

A) Asset intensity
B) Risk-return tradeoff
C) Same-store sales
D) Capital investment analysis

Same-store sales, also known as comparable-store sales, is the correct answer because it specifically refers to the revenue difference of a retailer's existing stores or sales channels over a certain period, compared to the same period in a previous year. This metric is used to evaluate the performance of a retailer's established locations, excluding the impact of opening new stores.