The correct answer is: C. Consumers surplus.
Consumer surplus is the difference between the maximum amount that a consumer is willing and able to pay for a good and the price that the consumer actually pays. It is a measure of the benefit that consumers receive from consuming a good.
The demand curve shows the relationship between the price of a good and the quantity of the good that consumers are willing and able to buy. The total area under the demand curve measures the total consumer surplus.
Marginal utility is the additional satisfaction that a consumer receives from consuming one more unit of a good. Total utility is the total satisfaction that a consumer receives from consuming all units of a good. Producer surplus is the difference between the minimum price that a producer is willing and able to accept for a good and the price that the producer actually receives.