一个Economics的问题

这里有人知道在经济里面Exit和Voice是什么意思吗？
我这里有定义，但是我还是不太明白
Exit:
An agent exercises exit behaviour by leaving a particulat market in response to an unsatisfactory standard of performance by a supplier.
Voice:
An economic agent can exercise voice by communicating an opinion to a supplier in a particular market without necessarily leaving that market.
有没有经济大虾小虾过来帮忙解释一下。
关于Voice这里还有到题目，
Which of the following types of behavior represent voice:
a, Buying a pasta from Safeway's rather than Morrison's.
b, Picketing laboratories that use animals for medical research.
c, buying a computer
d, b and c
路过的，帮忙看看，谢谢了。