心理定价策略
参考答案：是指根据不同类型的消费者在购买商品时的心理需求差异来给产品定价，以使消费者增加购买量，或者提高消费者作出购买决策的速度。
When he came back three hours later, they were still ____on the sofa, _____ in conversation.
A．sitting ; absorbing
B．sitting ; to absorb
C．seated ; absorbed
D．seated ; to be absorbed
铁路听觉信号，长声为（）。
A.2s
B.3s
C.4s
D.5s
