问题
单项选择题
A competitive firm will tend to expand its output as long as:（）
A. its marginal revenue is positive.
B. the market price is greater than the marginal cost.
C. its marginal revenue is greater than the market price.
答案
参考答案：B
解析：
A competitive firm faces a flat demand curve. This means the price is constant and the marginal revenue line is flat. A firm will continue to produce as long as MR ＞ MC, so the competitive firm will produce as long as P ＞ MC. It will stop when MC = MR = P.