Please answer both parts of this fixed income conceptual question:

3. When a bond indenture includes a sinking fund provision A. firms must establish a cash fund for future bond redemption. B. bondholders always benefit, because principal repayment on the scheduled a- turity date is guaranteed. C. bondholders may lose because their bonds can be repurchased by the corpora- tion at below-market prices. D. firms must establish a cash fund for future bond redemption and bondholders always benefit, because principal repayment on the scheduled maturity date is guaranteed. E. None of these is correct