Final answer:
Betterments, additions, or improvements to a revenue-producing facility are deposited to the Debt service reserve fund in a muni revenue bond trust indenture.
Step-by-step explanation:
In the case of a muni revenue bond trust indenture, betterments, additions, or improvements to a revenue-producing facility are typically deposited to the Debt service reserve fund. This fund is established to ensure that there are sufficient funds available to meet debt service obligations, including principal and interest payments, in case the revenues generated by the facility are not enough to cover them.