Answer: a counteroffer
Step-by-step explanation:
From the question, we are informed that Valley Farms offers to sell Whole Harvest Bakeries, Inc., five hundred bushels of wheat and that Whole Harvest responds by saying "We agree to buy five hundred bushels only if the wheat is Grade A quality."
The above statement is s counteroffer. A counteroffer is a response that is given based on an initial offer and it happens mostly when the initial offer is not accepted and therefore it is replaced with another offer.