During the period 1990 to 2017, the average yield on 3-month U.S. Treasury bills was 2.78%, the average inflation rate was 2.48%, the average yield on 30-year Treasury bonds was 5.22%, and the average return on 30-year Aaa - rated corporate bonds was 6.08%. The real risk - free short-term interest rate is OA. 2.13% B. 2.97% C. 0.30% OD. 4.76%