Long's Department Store Contracted to Buy 1,000 Drop-Waist Velour Dresses

Multiple Choice

Long's Department Store contracted to buy 1,000 drop-waist velour dresses in heather gray from Durham.Subsequently,Durham called and asked to ship mink-colored dresses instead of heather gray.Long agreed,in writing,to the change.Which statement is correct?

A) The modification is not enforceable since there was no consideration for the change.
B) The modification is not enforceable since the parties are merchants.
C) The modification is enforceable.
D) Whether the modification is enforceable depends on the gap-filler rule.