问题
单项选择题
Which of the following conditions exists when the economic gain to society is maximized（）
A. The sum of consumer and producer surpluses for a good or service is maximized.
B. The difference between consumer and producer surpluses for a good or service is maximized.
C. The price and quantity for a good or service is such that consumer and producer surpluses are equal.
答案
参考答案：A
解析：
In competitive market, the economic gain to society is maximized when the sum of the consumer and producer surpluses for a good or service is maximized.