生产工艺技术比选需要对比的经济指标包括( )。

A．占地面积、定员

B．产品收率、产品质量

C．单位产品投资、成本

D．国内外新技术和新成果

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.