问题
单项选择题
A perfectly competitive firm will not expand its output beyond the quantity where:（）
A. the market price is equal to its marginal cost.
B. its marginal revenue is positive.
C. the marginal cost is greater than marginal revenue.
答案
参考答案：A
解析：
A perfectly competitive firm will tend to expand its output so long as the market price is greater than marginal cost. In the short term and long term, profit is maximized when P = MC.