Which of the following statements is CORRECT? a. A debenture is a secured bond that is backed by some or all of the firm's fixed assets. b. Junk bonds typically provide a lower yield to maturity than investment-grade bonds. c. A company's subordinated debt has less default risk than its senior debt. d. Senior debt is debt that has been more recently issued, and in bankruptcy it is paid off after junior debt because the junior debt was issued first. e. Convertible bonds generally have lower coupon rates than non-convertible bonds of similar default risk because they offer the possibility of capital gains