问题如下：
The monopolistic competition has the characteristics of :
选项：
A.few firms
B.differentiated products
C.high barriers to entry and exit.
解释：
B is correct.
In monopolistic competition, products of a firm have slightly difference from its competitors. There is a large number of sellers and low barriers to entry.
考点： monopolistic competition
解析：垄断竞争厂商上的公司数量比较多，所以A选项不正确。
垄断竞争市场上的产品具备一定的差异化。所以B选项不正确。
垄断竞争市场上的进入和退出壁垒并不算高，所以C选项不正确。
能否请老师每一类的市场聚一个例子，
比如垄断性厂商，中石油
寡头厂商，移动、电信、联通
垄断竞争，手机厂商？
类似完全竞争，菜市场卖白菜的
不知是否能对应，便于理解记忆
