设栈S初始状态为空。元素a、b、c、d、e、f依次通过栈S，若出栈的顺序为c、f、 e、 d、b、a，则栈S的容量至少应该为______。

A．6

B．5

C．4

D．3

Is the computer          ? We don’t have          to buy it .

A．enough cheap , enough money

B．cheap enough , enough money

C．enough cheap , money enough

D．cheap enough , money enough