NO.PZ2018062003000068
问题如下：
In a market structure, if each firm’s supply function is well-defined, which of the following could it be?
选项：
A.
monopolistic competition.
B.
perfect competition.
C.
monopoly.
解释：
B is correct
In a market of perfect competition, a firm is viewed as a price taker, which supply function is determined by the marginal cost schedule.
考点：完全竞争市场特性
解析：在四类市场结构中，只有完全竞争市场的供给曲线是可以被定义描述的，它等于MC曲线大于AVC的那一段。
注意到，只有完全竞争厂商才有MR=P所以MC=MR=P, 在MC曲线上， P与产量方能对应。
但是对于其他类型的市场，P≠MR=MC,所以MC上点与产量对应不起来。所以只有完全竞争市场才存在这样的供给曲线。
为什么只有完全竞争市场P等于mc？不等于mc等于什么呢？
