Laetitia Agreed to Provide Certain Services to Hans in Exchange

Laetitia agreed to provide certain services to Hans in exchange for a payment of $10 000. Although Laetitia fully performed her side of the agreement, Hans refuses to pay anything. He insists that Laetitia does not have a right to sue for breach of contract because, in performing the services, she was merely doing something that she had become obliged to do even before she entered into her agreement with Hans. Hans' position is correct if Laetitia's pre- existing obligation was

A) some type of public duty.
B) for some reason enforceable.
C) a private obligation owed to a third party.
D) supported by a seal, rather than by consideration.
E) for some reason unenforceable.