Alvin Advertises on Craig's List to Sell His Used Lawnmower

Multiple Choice

Alvin advertises on Craig's List to sell his used lawnmower for $60. Roy tested the lawnmower and then offered Alvin $50 for it. In this case

A) the two parties have created a legally enforceable contract.
B) Roy's offer represents an acceptance of the original terms.
C) there is no agreement and no contract.
D) there is no agreement, but there is a valid contract.