After a wheat shortage that affected food supplies worldwide in 2008, a shortage of in the midwest caused concern about another global food shortage beginning in 2012.
a. corn
b. potatoes
c. soybeans
d. rice

The answer is
A. Corn.

In 2008, the world faced a food shortage crisis and especially of grains such as wheat. Making incorrect speculations and not reserving food should such a situation arise were considered as some of the factors. 

The midwest region of America is the heartland of corn-crop. corn is cultivated on a very large scale. The reason for this high demand and cultivation of corn was because of the demand for ethanol. The corn was not grown for edible purposes but to be used to acquire ethanol.