问题如下：
Country A’s regulatory department is planning on taking measures to help promote its market efficiency, which of the following actions would not be helpful of country A to reach its goal?
选项：
A. Restrict short selling.
B. Release restriction for unrestricted foreign investor to trade.
C. Issue penalties to insiders for using unfair nonpublic information.
解释：
A is correct.
Permitting foreign investor trading and penalizing insider trading would both encourage greater market participation and hence would increase market efficiency. However, restricting short selling would reduce arbitrage and impede market efficiency.
老师，A不是应该妨碍市场效率吗？而且C为什么不对？
