Answer : b. the nominal rate of interest is the real rate of interest plus the rate of inflation; lenders need to raise the nominal rate when inflation increases to maintain their desired real return.
Explanation: Nominal rate = real rate + inflation . Suppose they had an real return of 4% when the inflation was 1% and they charged at credit card rate at 5%. Now if the inflation increases to 2%, the cannot continue to charge 5% since in that case their real return would only be 3%. Hence they will now have to charge 6% to still get their original real rate of 4%