The Market Demand Curve, with Price on the Vertical Axis

The market demand curve, with price on the vertical axis and quantity on the horizontal axis, is determined by

A) adding individual demand curves in a horizontal direction.
B) adding individual demand curves in a vertical direction.
C) subtracting the demand for the product from the supply of the product.
D) adding the demand for the product and the supply of the product.
E) subtracting supply from demand at each price.