Because of successful advertising: Choose one: A. there is only one firm that produces a product for which there are no good substitutes O B. there are many sellers in the market and each is small relative to the total market. O C. the demand curve facing each firm shifts right, while the cost curves shift upward D. the decisions of one seller often influence the prices of products, the output, and the profits of rival firms OE. the demand curve facing each firm shifts right, while the cost curves shift downward