向各位大侠请教一个关于natural level of output的问题。prof给了一个选择题，题面如下：

Which of the following would cause an increase in the natural level of output?
A. A decrease in government spending
B. A decrease in taxes
C. An increase in the money supply
D. None of the above


给出的答案是D，我自己选择了B。但是我不理解为什么B是不对的。哪位高人能否指点一下？

谢谢！