Supply and Demand

What effect is working when the price of a good falls and consumers tend to buy it instead of other goods ?

A. The ceteris paribus effect
B. The diminishing marginal utility effect.
C. The substitution effect
D. The income effect

The law of demand implies that ?

A. as prices rise, demand decrease
B. as prices fall, quantity demanded increase
C. as prices fall demand increases
D. as prices rise, quantity demanded increases