A corporation issued a 20 year, 5% coupon bond 8 years ago. Over those 8 years, interest rates generally have fallen, and the corporation's bond rating has increased from BBB to AAA. As a result, the YTM has fallen. Based on these developments...
A. The coupon rate remains unchanged
B. The coupon rate has increased
C. The coupon rate has decreased
D. The company does not have to pay a coupon now