()是企业进行行业比较、选择的价值标准，所以也称为行业价值。
A．行业吸引力
B．竞争能力
C．购买者讨价还价能力
D．新进入者的威胁
参考答案：A
I realize she can be very troublesome, but ______I think you should apologize for being so angry with her.
A．all the same
B．once in a while
C．in actual fact
D．all the time
设a和b是两个常数，积分区域D=(x，y)||x|+|y|≤1，则
=______．
=______．