厂商的超额利润为零，说明了（）
A.正常利润为零
B.正常利润大于零
C.应该停止营业
D.价格等于平均成本
E.价格大于平均成本
参考答案：B, D
— Why! I _____ get you on the phone.
— We ______ basketball on the playground when you phoned.
A．didn't; must be playing
B．couldn't; must be playing
C．couldn't; must have played
D．didn't; must have been playing
小企业首笔信贷业务必须实行（）。
A.双人实地调查
B.双人管户
C.调查、审查岗联合评估
D.以上答案都不正确
