Answer:
illusory promise
Explanation:
An illusory promise is a promise that doesn't constitute a valid contract. It is not enforceable because it lacks mutuality. In common law, the acceptance must be a mirror image of the offer in order for a valid contract to exist. Dan didn't really accept the offer, since he included the condition " if he does not find one that he likes more" which is very ambiguous and not something definite.
