Some countries have fixed exchange rate systems instead of flexible exchange rate systems. Which of the following is a reason why fixed exchange rate systems have limited abilities to use monetary policy? A. Under a fixed exchange rate system, if a central bank conducts a monetary policy, there is no change in domestic interest rates because people only respond to exchange rate changes. B. Under a fixed exchange rate system, if a central bank conducts a monetary policy, then it puts pressure on the exchange rate and the central bank would have to offset that effect. C. Under a fixed exchange rate system, central banks do not exist so monetary policy cannot be conducted. D. All of the above.