Mortgage bonds are backed by$-$Select$-$current assetsfixed assetsmarketable securitiesItem $14.$ First mortgage bonds are senior in priority to claims of second mortgage bonds. Debentures are long$-$term bonds that are not secured by a mortgage. Subordinated debentures are bonds having claims on assets only after senior debt has been paid in full in the event of liquidation.$-$Select$-$Secured$-$debentureInvestment$-$gradeItem $15$ bonds are rated triple B or higher, and many banks and other institutional investors are legally limited to only holding these bonds. In contrast, junk bonds are high$-$risk, high$-$yield bonds.