Farmer entered into a four-year written requirements contract with Brewer. Under the contract, which was signed by both parties, Farmer was to provide Brewer with all the wheat, barley, and hops it needs for its production over the next four years. Another term provided that "all natural ingredients are to be grown and purchased in accordance with the side oral agreement agreed to by the parties." ("All Natural Ingredient" clause) The side oral agreement was an agreement by both parties to follow the growing standards for "natural ingredients" under the Federal "Natural Ingredients Act." In the third year of the contract, Brewer rejected the wheat, barley, and hops tendered by Farmer because he alleged the ingredients were not "natural" as specified in the All Natural Ingredient" clause.

In an action by Farmer for breach, can Brewer admit the side oral All Natural Ingredient agreement into evidence to show that its rejection of Farmer's ingredients was proper?

(A) No, because the parol evidence rule will bar its admission.

(B) No, unless the court finds the written contract only partially integrated.

(C)Yes, because the All Natural Ingredient clause in the written agreement is ambiguous on its face and use of the standards of the "Natural Ingredients Act" is a reasonably susceptible interpretation of the agreement under the circumstances.

(D) Yes, because the side oral All Natural Ingredient agreement is not parol evidence.