A profit maximizing firm will expand output as long as marginal revenue is:（）
A. less than marginal cost.
B. greater than marginal cost.
C. less than average variable cost.
参考答案：B
解析：
A purely competitive firm will tend to expand its output so long as the market price (marginal revenue) is greater than marginal cost. In the short term and long term, profit is maximized when P = MC.
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