Answer:
evidence of oral agreement that merely explains the meaning of written terms without changing the terms.
Explanation:
The parol evidence rule describes that that case related to the parties are introduced into the court that means the evidence in order to change it, explain it at issue time.
So as per the given situation, since the question ask the exception to this rule so the first option is correct as in this it is mentioned that the terms would remain unchanged
Therefore the first option should be considered