What does the parol evidence rule state about contracts?

The parol evidence rule primarily addresses the admissibility of oral or extrinsic evidence in relation to written contracts. This principle posits that if there is a written contract that is intended to be a complete and final expression of the parties' agreement, then any prior or contemporaneous oral agreements or negotiations that contradict or modify the written contract cannot be introduced to alter its meaning. However, it does allow for the introduction of oral evidence to clarify or complete the contract if it is ambiguous or incomplete.

Thus, the correct choice highlights that oral evidence can indeed supplement a written contract when the writing does not capture all aspects of the parties' agreement, allowing for clarification or completion of the terms. This feature of the parol evidence rule helps ensure that contracts are interpreted in a way that reflects the true intentions of the parties, especially when a written document might not fully encapsulate all elements of the agreement.