问题如下：
According to the theory of money neutrality, money supply growth does not affect variables such as real output and employment in:
选项：
A. the long run.
B. the short run.
C. the long and short run.
解释：
A is correct.
According to the theory of money neutrality, an increase in the money supply ultimately leads to an increase in the price level and leaves real variables unaffected in the long run.
考点： Money neutrality
解析：货币中性的观点认为在长期，超额的货币供给只会带来物价的上涨而不会对诸如产出、就业等有关真实经济变量造成改变。
但是在短期，货币供给的增发还是可以刺激总需求，从而暂时拉抬一国经济的发展。
为什么不选c呢？货币供给短期会改变v和y吗
