Jack and Jill Are Friends

Jack and Jill are friends.Jack agrees to mow Jill's lawn and Jill agrees to pay Jack $50.00.Jill wants the lawn mowed by April 1.Jill returns on April 3 and finds that the lawn has not been mowed.Jill,who is entertaining the next day,goes to Jack and promises that if he mows the lawn that day,she will give him an additional $20.00.Jack mows the lawn but Jill refuses to pay him the additional $20.00.Which of the following is true?

A) Jack can sue Jill for breach of contract.
B) Jill has no obligation to pay because the promise to pay the additional $20.00 was not supported by fresh consideration.Jack had a pre-existing legal duty to mow the lawn.
C) There was no offer and acceptance.
D) Jill has an obligation to pay the additional $20.00 because a legally enforceable promise to pay was made.
E) Jill made an offer and Jack accepted it,so a contract was created.