NO.PZ2018062003000074
问题如下：
In a market of perfect competition, if economic profits are accessible to companies. In the long run, the supply curve is most likely to:
选项：
A.
stay the same.
B.
shift to the right.
C.
shift to the left.
解释：
B is correct
New competitors will be attracted to the market by economic profits, and the existing companies will be encouraged to expand production.
考点：完全竞争市场
解析：由于存在不菲的利润，所以这些利润会吸引外部的厂商进入该市场分一杯羹，同时原有厂商也会进一步扩大生产，两者都会导致行业供给增加，供给曲线向右平移。
1、从长期来看，厂商会达到长期均衡，此时economic profit=0，这个不会导致厂商退出从而使市场供给减少吗？
2、图中DWL代表什么？
