NO.PZ2022071403000058
问题如下：
Question
If the central bank buys securities from banks in its open-market operations when the economy is already in long-run equilibrium, which of the following is most likely to occur?
选项：
A.The aggregate demand curve will shift to the left. B.The long-run supply curve will be unaffected, but the price level will rise. C.Both the long- and the short-run aggregate supply curves will shift to the right.解释：
Solution
B is correct. When the central bank buys securities from banks in an open-market operation, it pays for them with a corresponding increase in bank reserves. This increases the amount of deposits banks can accept from their customers—that is, the money supply. An expansionary monetary policy will cause the aggregate demand curve to shift to the right. The short-run supply curve will also shift to the right because input prices do not initially adjust upward. In time, prices will increase, causing the short-run aggregate supply curve to steepen and eventually return to the long-run natural level of output—but at higher prices.
A is incorrect. The purchase of securities by the central bank results in an increase in money supply, which will result in lower interest rates, higher investment, and possibly higher consumption, causing the aggregate demand curve to shift to the right.
C is incorrect. The purchase of securities by the central bank results in an increase in money supply. Initially, the short-run aggregate supply curve will shift to the right because prices are fixed, but as prices rise, output will return to its long-run natural level, leaving the long-run supply curve unchanged.
中文解析：
B正确。当央行在公开市场操作中从银行购买证券时，它以相应增加的银行准备金来支付这些证券。这增加了银行可以从客户那里接受的存款金额，也就是货币供应量。扩张性货币政策将导致总需求曲线向右平移。短期供给曲线也会向右平移，因为投入价格最初没有向上调整。随着时间的推移，价格会上涨，导致短期总供给曲线变陡，最终回到长期自然产出水平——但价格会更高。
A不正确。中央银行购买证券导致货币供应量增加，从而导致利率降低，投资增加，并可能导致消费增加，使总需求曲线向右平移。
C选项不正确。中央银行购买有价证券导致货币供应量增加。最初，短期总供给曲线会向右平移，因为价格是固定的，但随着价格的上升，产出会回到长期自然水平，使长期供给曲线保持不变。
可不可以麻烦老师用图像画一下大概的情况呢？谢谢
