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 consumers' preferences for corn.
B) An increase in the labour costs of producing corn.
C) An increase in consumers' income if corn is a normal good.
D) An improvement in the technology of producing corn.
E) An increase in consumers' income if corn is an inferior good.