Which of the following leads to a lower level of unemployment in the long run?
A、both an increase in the size of the money supply and an increase in the money supply growth rate
B、an increase in the size of the money supply but not an increase in the money supply growth rate
C、an increase in the money supply growth rate, but not an increase in the size of the money supply
D、neither an increase in the size of the money supply nor an increase in the money supply growth rate