问题如下：
In an industry comprised of three companies, which are small-scale manufacturers of an easily replicable product unprotected by brand recognition or patents, the most representative model of company behavior is:
选项：
A. oligopoly.
B. perfect competition.
C. monopolistic competition.
解释：
B is correct.
The credible threat of entry holds down prices and multiple incumbents are offering undifferentiated products.
考点：市场结构
解析：题目说到市场中的商品是没有专利的，在这种情况下，市场上的不同厂家生产的产品基本也是同质的，虽然目前市场上的厂家数量比较少，但是由于没有门槛限制，所以厂商可以自由进入，退出。那么这种情况最符合完全竞争市场的特点。
请问垄断竞争的进出和退出壁垒也是很低的，为什么不选它
相关特征要记一下，请知悉