Answer:
a. serial bonds
Step-by-step explanation:
Serial bonds are different from term bonds in that, the former do not mature on a single date; this means that the principal amount(amount borrowed) is repaid in small portions at periodic dates and this occurs throughout the life of the bond. These serial bonds are commonly issued by municipal bond issuers. On the other hand, term bonds have specific maturity date and that is when the face value is payable.