NO.PZ2018062003000109
问题如下：
If the energy price increases sharply, in the long run the overall price level will:
选项：
A.keep raising if the central bank takes no steps.
B.stay unchanged as long as the money supply doesn’t increase.
C.keep raising until all prices have increased by the same proportion.
解释：
B is correct.
If the money supply is not expanded by the central bank, and the aggregate demand curve doesn’t change, downward pressure will be brought to the input price level back. In the long run, the price level tends to stay unchanged.
考点：AS曲线
解析：能源价格的攀升会造成总供给的衰退，总供给的衰退在长期会引起原材料价格的下降，从而使得总供给恢复到初始水平。这期间，如果该国央行不实施干预，那么总需求就不会发生改变。
总供给和总需求在长期都未改变的结果就是物价水平保持不变。
请问题目解析的意思是短期和长期，央行不干预的情况下总需求曲线都不会发生改变吗？
央行干预的话会两条曲线又会发生怎样的变化呢？
