Cut-Rate Construction Company (CCC) Begins Building a Restaurant for Diners

Cut-Rate Construction Company (CCC) begins building a restaurant for Diners Restaurants, Inc., but after two months demands an extra $100,000. Diners agrees to pay.
-Refer to Fact Pattern 11-3.If CCC offers,as a reason for the extra $100,000,that extraordinary unforeseen difficulties will add considerable cost to the project,the agreement is

A) enforceable as an accord and satisfaction.
B) enforceable because of unforeseen difficulties.
C) unenforceable as an illusory promise.
D) unenforceable due to the preexisting duty rule.