问题如下：
Suppose a central bank decides to maintain a target exchange rate.What will happen when its inflation rate falls below the level of the inflation rate in the target country?
选项：
A.The central bank will sell the domestic currency.
B.The interest rates will increase.
C.The domestic money supply will decrease.
解释：
A is correct.
In this scenario,the central bank would need to sell the domestic currency to support the target,tending to increase the domestic money supply and reduce the interest rate.
考点：货币政策
解析：
本国通胀率低于目标国的通胀率会导致本国的汇率上升，为了保证本国货币不升值，必须实施一个扩张（升通胀）的货币政策。
A选项卖出本国货币，类似于向市场提供货币供给，是一个扩张的货币政策，入选。
B选项利率上升是一个紧缩的货币政策，不入选。
C选项减少货币供给也是紧缩的货币政策，不入选。
请问为什么要保证本国货币不升值呢，升值不是好事吗
