Which If the Following Describes a Product-Market Most Accurately

Which if the following describes a product-market most accurately?

A) Exchanges are based on barter rather than money.
B) One seller has a patent for a superior product and other firms try to imitate the leader the best they can.
C) All the customers want the same product but will consider a substitute if their preferred brand is not available.
D) Competing sellers offer physically or conceptually similar products.
E) No intermediaries operate in the market.