Which type of bonds would user charges be used to service?

User charges are specific fees collected from individuals or businesses that utilize a service or facility, which generate revenue that can be used to repay borrowed funds. In the context of bonds, revenue bonds are specifically designed to be repaid from the income generated by the projects that they finance. For example, a toll road or a public utility may issue revenue bonds, where the tolls collected or utility fees charged directly service the debt.

In contrast, general obligation bonds are typically secured by the full faith and credit of the issuing municipality and are paid for through general taxation rather than user fees. Convertible bonds represent a hybrid security that can be converted into equity, and while municipal bonds can include both revenue and general obligation bonds, they do not exclusively rely on user charges for servicing debt. Thus, revenue bonds are the correct choice in this context, as they directly depend on the revenue generated from user charges for their repayment.