客户购买的总价值与客户购买的总成本之间的差额我们称之为（）。
A.客户让渡价值
B.客户关系价值
C.客户满意价值
D.客户服务
参考答案：A
做教学准备工作，只要备好课写好教案就可以了。 （ ）
A ship must have a self-contained breathing apparatus to be used as protection from gas leaking from a refrigeration unit. To meet this requirement，you may use（）.
A.a gas mask certified by the Mine Safety and Health Administration
B.the same self-contained breathing apparatus required with the fireman's outfit
C.an oxygen breathing apparatus，provided that the device has been inspected within three years
D.a portable ventilation system that will provide a complete change of air every three minutes
