Blaw question

Bradley is sitting on his porch enjoying his very large front yard and drinking a lemonade when Chris, a kid from down the street, shows up and starts mowing Bradleys yard. Bradley waives and smiles. Chris is mowing the lawn for money, but Bradley doesnt know it (and shouldnt know it because their two families often do nice things for each other without pay). Chris may be able to recover money from the courts on the basis of a(n):

a. express contract.

b. bilateral contract.

c. implied contract.

d. quasi contract.