-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) a decrease in the number of corn growers
B) a decrease the price of wheat,a substitute in production for corn
C) an increase in the cost of the seed used to grow the corn
D) a decrease in buyers' incomes if corn is an inferior good
E) an increased belief among buyers that corn is healthy