问题如下：
A currency portfolio manager believes that actively trading currencies are costly because of the management fee and transaction costs, and in the long tun the currency market is a zero-sum game. The manager will most likely choose:
选项：
A.not hedging currency risk.
B.discretionary hedging
C.currency overlay
解释：
A is correct.
考点：reasons of hedge/not hedging currency risk
解析：not hedge currency risk的原因有：hedge是有成本的，即使hedge也不一定可以获得超额收益；从长期来看，有效市场是零和游戏，一种货币升值，那另一种货币肯定是贬值的；外汇在长期将趋于fair value。这个投资经理的观点符合前两条，所以不会hedge。Discretionary hedging和currency overlay是hedge currency risk的两种策略，所以BC不对。
老师，题目答案中“从长期来看，有效市场是零和游戏，一种货币升值，那另一种货币肯定是贬值的；”。不是很明白为什么是不hedge的理由，这种情况下是说明hedge没用么？
