问题
单项选择题
A monopolist will continue expanding output as long as:（）
A. marginal revenue is positive.
B. marginal revenue is greater than marginal cost.
C. average total costs are declining.
答案
参考答案：B
解析：
The optimum behavior of all firms is to produce until the point where MR = MC. So, the monopolist can increase total profit by increasing production as long as marginal revenue is greater than marginal costs.