What is one effect of the Parol Evidence rule?

The Parol Evidence Rule is a significant principle in contract law that primarily serves to preserve the integrity of written agreements. It establishes that once parties have reduced their contract to writing, any prior oral agreements or negotiations that contradict, modify, or add to the written terms cannot be considered in court. This ensures that the written contract is viewed as the complete and final expression of the parties' agreement.

Given this context, the correct answer reflects that the Parol Evidence Rule prohibits the inclusion of prior oral agreements in written contracts. This serves to protect the sanctity of the written document, preventing parties from arguing claims based on discussions or understandings that occurred before the contract was finalized. This rule thus reinforces that the written contract holds prevailing authority over any informal verbal negotiations or agreements that may have taken place beforehand.