单选题 Under perfect competition, a firm will be inclined to increase output as long as which of the following conditions exists?

A、 Marginal revenue is greater than marginal cost.
B、 Marginal cost is less than average cost.
C、 Marginal revenue is positive.

【正确答案】 A

【答案解析】A firm will continue to expand output as long as it is possible to earn an economic profit. In other words, a firm will expand output as long as marginal revenue is greater than marginal cost.