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。
这道题事怎么看出对as曲线问题提问的呢？题目中只谈到能源看价格快速上涨问价格水平水平如何变化
