Final answer:
The term 'maturity' is not a type of bond but rather refers to the maturity date of a bond, making it the option that does not represent a type of bond.
Step-by-step explanation:
To address the question about which option is not a type of bond, we can analyze each term individually. A maturity bond refers to the maturity date, the date by which a borrower must repay a bond. Commodity-backed bonds are a type of security that is backed by a specific physical commodity and hence commodity backed would be a plausible term related to bonds. A serial bond is a bond that matures in installments over a period of time. A term bond is a bond that matures on a specific date in the future. Out of the provided choices, 'maturity' does not directly represent a type of bond but rather a feature of most bonds, which is their maturity date.