Assuming exchange rates are allowed to fluctuate freely, which one of the following factors would likely cause a nation’s currency to appreciate on the foreign exchange market?

a. A relatively rapid rate of growth in income that stimulates imports.

b. A high rate of inflation relative to other countries.

c. A slower rate of growth in income than in other countries, which causes imports to lag behind exports.

d. Domestic real interest rates that are lower than real interest rates abroad.