Final answer:
An agreement to gift a car would not be enforceable without additional consideration because a gift lacks the exchange of value required for a binding contract.
Step-by-step explanation:
The question asks which of the given options would not be enforceable without additional consideration. Consideration is a legal term referring to something of value exchanged between parties in a contract. It's a necessary component for a contract to be considered valid and binding. In the options provided, an offer to sell goods, a contract to purchase land, and a promise to pay a debt are all typically enforceable as they inherently involve the exchange of consideration. However, an agreement to gift a car lacks consideration because a gift is a voluntary transfer of property from one person to another without anything of value being exchanged in return. For a gift to be enforceable, there must be additional consideration or the gift must be completed (delivered and accepted).