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。
完全竞争的曲线是水平的，如何右移呢？即使右移也是水平啊？