Which of the following statements is correct? a. one disadvantage of zero coupon bonds is that the issuing firm cannot realize any tax savings from the debt until the bonds mature. b. once a firm declares bankruptcy, it must then be liquidated by the trustee, who uses the proceeds to pay bondholders, unpaid wages, taxes, and lawyer fees. c. a firm with a sinking fund that gave it the choice of calling the required bonds at par or buying the bonds in the open market would generally choose the open market purchase if the coupon rate exceeded the going interest rate. d. income bonds must pay interest only if the company earns the interest. thus, these securities cannot bankrupt a company prior to their maturity, and this makes them safer to the issuing corporation than "regular" bonds. e. other things held constant, a callable bond should have a lower yield to maturity than a noncallable bond.