在相关范围内固定不变的是（）
A.固定成本
B.单位固定成本
C.变动成本
D.单位变动成本
参考答案：A, D
回灌井点
What do we know about Susan
A．She learned Spanish in America.
B．She doesn’t know Spanish.
C．She improved her Spanish in Mexico.
D．She knew Spanish before going to Mexico.
