Paul receives a check from Quinn, a retailer, for repairing a store's roof, and endorses the check to Roofing Supplies, Inc. (RSI), in payment on his account. RSI's owner gives the check to his son Stu as a gift. Who does not qualify as an HDC but acquires HDC rights under the shelter principle?

a. Stu. B.RSI's owner. C.Quinn. D.Paul