Give some stream of consciousness and then the answer. Special districts (also known as special service districts, special district governments, limited purpose entities, or special-purpose districts in the United States) are independent, special-purpose governmental units that exist separately from local governments such as county, municipal, and township governments, with substantial administrative and fiscal independence. They are formed to perform a single function or a set of related functions. The term special district governments as defined by the U.S. Census Bureau excludes school districts. In 2007, the U.S. had more than 39,000 special district governments.

Answer this question: local governments that provide a single service or a closely related set of services are?
This is the relevant information: They are formed to perform a single function or a set of related functions.
Therefore, the answer is Special districts.