Which of the following actions can lead to an unenforceable oral contract?

An unenforceable oral contract often arises from certain legal requirements that need to be satisfied for specific types of agreements. One primary example is contracts concerning the sale of real estate. Generally, in most jurisdictions, any agreement that involves the sale of property must be in writing to be enforceable under the Statute of Frauds. This means that if a contract for the sale of property is only made orally, it cannot be enforced in a court of law, making it unenforceable.

In contrast, the presence or absence of witnesses (as in the first choice) does not affect the enforceability of an oral agreement for most types of contracts outside of a few exceptions. Choosing options involving negotiations in writing or discussing terms over dinner (like the third and fourth choices) also do not automatically lead to unenforceable agreements. Written negotiations can lead to valid contracts once terms are agreed upon, and discussions alone don't constitute a binding agreement unless specific legally binding terms have been established. Thus, contracting for the sale of property, being a category specifically requiring written documentation, directly leads to the situation described.