请问市场中性不是对短期有影响，长期没有影响吗？为什么选B

问题如下：

Which of the following best describes a fundamental assumption when monetary policy is used to influence the economy?

选项：

A.

Financial markets are efficient.

B.

Money is not neutral in the short run.

C.

Official rates do not affect exchange rates.

解释：

B is correct.

If money were neutral in the short run, monetary policy would not be effective in influencing the economy.

考点： Money neutrality

解析：如果货币中性在短期发生，那么在短期货币供给不能影响经济中的真实变量，那么货币政策就是无效的，所以B选项说法正确。

A选项没有B选项好，如果金融市场不有效，货币政策多多少少也会有点作用，但是一旦货币中性在短期发生，那么货币政策就一点效果也没有。

C选项是一个打酱油的选项，错误。