How Will the Exchange Rate (Foreign Currency Per Dollar)respond to a Decrease

How will the exchange rate (foreign currency per dollar) respond to a decrease in the relative rate of productivity growth in Canada in the long run?

A) Exchange rates will rise.
B) Exchange rates will fall.
C) Exchange rates will be unaffected by changes in the relative rate of productivity growth in Canada, both in the short run and in the long run.
D) The exchange rate will be affected in the short run, but not in the long run.