Which of the following is (are) NOT true? a) All are true. b) Zero coupon bonds typically sell at a deep discount initially and do not pay interest. c) An issuers failure to make required interest or principal payments on outstanding bonds can result in bankruptcy. d) A sinking fund is an account managed by a trustee for the sole purpose of redeeming (paying off or retiring) bonds prior to their maturity. e) Bond covenants (like limiting dividends or requiring specific levels of working capital) are put in place to protect investors