Secured bonds have which of the following features:

A$.$ Not backed up by an asset, the interest and principal are paid at maturity.

B$.$ Backed up by an asset, the interest and principal are paid at maturity.

C$.$ Backed up by an asset, the interest is paid throughout the life of the loan, and the principal is paid at maturity.

D$.$ Backed up by an asset and a set principal and interest payment is made throughout the life of the loan.