The table above lists the market shares of the twenty makers of personal computers. The four-firm concentration equals

Under which one of the following market structures are sellers most likely to consider the reaction of rival sellers when they set the price of their product?

A. Perfectly competition. B. Monopoly. C. Monopolistic competition. D. Oligopoly.

Economic activity moves from a trough into a period of ________ until it reaches a ________ and then into a period of ________.

A. recession; peak; expansion B. recession; trough; expansion C. expansion; trough; recession. D. expansion; peak; recession