Suppose the Market Demand Curve for a Good Passes Through

Suppose the market demand curve for a good passes through the point (quantity demanded = 100, price = $25) . If there are five buyers in the market, then

A) the marginal buyer's willingness to pay for the 100th unit of the good is $25.
B) the sum of the five buyers' willingness to pay for the 100th unit of the good is $25.
C) the average of the five buyers' willingness to pay for the 100th unit of the good is $25.
D) all of the five buyers are willing to pay at least $25 for the 100th unit of the good.