Buyer, Inc., contracted in writing with Shareholder, who owned all of XYZ Corporation's outstanding stock, to purchase all of her stock at a specified price per share. At the time this contract was executed, Buyer's contracting officer said to Shareholder, "Of course, our com- mitment to buy is conditioned on our obtaining approval of the contract from Conglomerate, Ltd., our parent company." Shareholder replied, "Fine. No problem." Later, Shareholder was willing and ready to consummate the sale of her stock to Buyer, but the latter refused to perform on the ground (which was true) that Conglomerate had firmly refused to approve the contract. If Shareholder sues Buyer for breach of contract and seeks to exclude any evidence of the oral condition requiring Conglomerate's approval, the court will probably (A) admit the evidence as proof of a collateral agreement. (B) admit the evidence as proof of a condition to the existence of an enforceable obligation, and therefore not within the scope of the parol evidence rule. (C) exclude the evidence on the basis of a finding that the parties' written agreement was a complete integration of their contract. (D) exclude the evidence as contradicting the terms of the parties' written agreement, whether or not the writing was a complete integration of the contract.