A．They save a lot of money in their daily budgets.
B．They are clever than other people because they buy something with less money.
C．They made unnecessary purchase because of the low price.
D．They feel unhappy after purchasing because they don't need what they buy.

A．teach people how to control their behavior.
B．punish people who have some problems.
C．form a habit of saving money.
D．test their ability of bargaining.