用于描述偏态分布的计量资料型数据集中趋势的统计学指标是( )

A．均数

B．几何均数

C．中位数

D．标准差

Compared to a competitive market, a monopoly situation will produce:（）

A. less output, and the sum of the consumer surplus and the producer surplus will be reduced.

B. more output, and the sum of the consumer surplus and the producer surplus will be reduced.

C. less output, and the sum of the consumer surplus and the producer surplus will be increased.