在范里安的中级微观经济学里，

But if they could both just hang tight, they would each be better off! If they both could be sure the other would hold out, and both could agree to hold out themselves, they would each get a payoff of −1, which would make each of them better off. The strategy (deny, deny) is Pareto efficient—there is no other strategy choice that makes both players better off—while the strategy (confess, confess) is Pareto inefficient.

好像只讲了一个帕累托最优。

但是，看了知乎大神的回答，有三个帕累托最优。

https://www.zhihu.com/question/30893365


不知道要怎么理解另外两个是帕累托最优的情况。为什么【defection，confess】【confess，defection】也是帕累托最优？
求帮助！！！