One Reason That the Quantity Demanded of a Good Tends

One reason that the quantity demanded of a good tends to rise as its price falls is that:

A) the decrease in price shifts the supply curve downward.
B) people feel a bit richer and increase their use of the good.
C) demand has to rise to restore equilibrium after a price reduction.
D) suppliers are willing to supply more at lower prices.
E) the decrease in price shifts the demand curve upward.