To Find the Market Demand Curve for In-Line Skates, We

To find the market demand curve for in-line skates, we must

A) take account of the skate buying plans of all actual and potential buyers in all possible situations.
B) add the quantities demanded at every price and every income by every buyer of in-line skates.
C) sum horizontally the individual demand curves of all the buyers.
D) add the quantities demanded at prices that all buyers can afford to pay.
E) None of the above answers is correct because we need also to take account of the supply of in-line skates.