The Above Figure Illustrates the Market for Corn

The above figure illustrates the market for corn. If point "a" represents the original equilibrium and point "b" the new equilibrium, which of the following could have caused the change?

A) an increase in income if corn is a normal good
B) an increase the price of wheat, a substitute in production for corn
C) an increase in the cost of the fertilizer used to grow the corn
D) a belief among corn farmers that the price of a bushel of corn will be higher next month
E) an increase in the number of corn growers