Suppose You Observe a Decrease in the Equilibrium Price and Quantity

Suppose you observe a decrease in the equilibrium price and quantity of corn. Of the options listed below, this is best explained by:

A) a decrease in the cost of growing corn.
B) an increase in the cost of growing corn.
C) a rise in consumer income assuming corn is a normal good.
D) a fall in consumer income assuming corn is a normal good.