NO.PZ2022090802000004
问题如下：
Which of the following businesses is least likely to have network effects?
(备注：原版书课后题原题。和真题的出题形式不同（真题只有三个选项）。大家做题时不用纠结题目形式，关注知识点原理即可)
选项：
A.A stock exchange
B.A telephone company
C.A classified advertising website; A price comparison website for travel airfares
D.A resume preparation service for online job seekers
解释：
Solution
D is correct. The resume preparation service benefits from the network effects on various online job sites, but the service is not the source of those network effects. Each of the other businesses (A, B, C) becomes more valuable to its customers as it attracts users. A stock exchange is valuable and worth joining because many securities trade on it. The telephone network is very useful because most people are on it. A classified advertising website becomes more useful as it attracts more listings. An airfare price comparison website is valuable to airlines because it has many shoppers and valuable to shoppers because it features prices for multiple airlines and routes.
讲义上说选项D属于two sided or more groups users，为什么这里又归位不属于network effect，这个知识点理解得很混乱，可否请老师梳理总结具体例子
