Final answer:
The seller keeps the Bill of Sale until the purchase price is paid according to the contract. Therefore, the correct option is D. Bill of sale.
Step-by-step explanation:
In the goods market, the seller keeps the Bill of Sale until the purchase price is paid according to the contract. A Bill of Sale is a legal document that records the sale of goods between a seller and a buyer. It includes important information such as the description of the goods, the purchase price, and the terms and conditions of the sale.