Under a Contract with Red Wines, Sancho Begins Grading a Terraced

Multiple Choice

Under a contract with Red Wines, Sancho begins grading a terraced hillside for the planting of grapes. Halfway through the project, Sancho asks for $5,000 over the contract price, claiming an increase in the "cost of doing business." Red agrees but later refuses to pay. Red's agreement to pay more is

A) unenforceable because Sancho's performance was a preexisting duty.
B) unenforceable because Red's promise was illusory.
C) enforceable.
D) unenforceable because Sancho's request modified the contract.