Looking back their senior school life, many university students said they____have wasterd so much time on computer games then.

A．couldn’t

B．wouldn’t

C．needn’t

D．shouldn’t

服务量增至边际成本（）边际收入时，为企业获得其最大利润的服务量。

A、大于

B、等于

C、小于

D、不等于