Why Are Most Demand Curves Downward Sloping

Multiple Choice

Why are most demand curves downward sloping?

A) consumers get tired of goods and use less of them.
B) consumers want more variety in goods and services.
C) a higher price for a good reduces the consumer's desired consumption of a good.
D) a lower price for a good reduces the consumer's desired consumption of a good.
E) none of the above.