Baked Stuff Company Agrees to Supply Comida Café with All

Baked Stuff Company agrees to supply Comida Café with all the corn chips that it requires for a year.A sudden blight caused by an organism hitherto unknown in the United States results in a shortage of corn,and the price rises sharply.Baked Stuff asks Comida to pay a higher price for the chips.This request is

A) invalid as an attempt at extortion or the so-called holdup game.
B) invalid under the preexisting duty rule.
C) valid as a risk ordinarily assumed in business.
D) valid due to the unforeseen difficulty of the sudden price increase.