What does the parol evidence rule prevent?

The parol evidence rule is a legal principle that determines the extent to which parties to a written contract may introduce external evidence, such as oral statements or prior written agreements, to interpret or contradict the terms of that written agreement. This rule is based on the idea that once parties have reduced their agreement to writing, any prior negotiations or agreements which contradict the written terms should not be considered because the written contract is presumed to represent the complete and final understanding of the parties.

In this context, the correct answer highlights the significance of the written contract as a final expression of the parties' intentions, thereby preventing the introduction of external evidence that would undermine or contradict what is explicitly stated in that written contract. This safeguard ensures the integrity of written agreements and prevents ambiguity arising from conflicting evidence.

The other options do not accurately reflect the core function of the parol evidence rule. It does not prevent the introduction of new contracts during negotiations nor does it limit the ability of parties to modify existing contracts through subsequent agreements. Furthermore, the parol evidence rule does not address the withdrawal of a party from a contract, as that relates more to the concepts of contract termination and breach rather than the admissibility of evidence.