Which one of the following is NOT included in community water systems?

Community water systems are defined as systems that provide water for human consumption to at least 15 service connections or regularly serve at least 25 individuals. These systems can be operated by different types of entities, including municipalities, non-profit organizations, or private companies. However, when considering what constitutes a community water system, it's important to recognize that private companies that provide water services do not typically fall under the category of community water systems as defined by regulatory standards.

Municipal utility districts, mobile home parks, and rural water supply corporations are all included in the context of community water systems because they are established to serve specific communities or groups of people. Municipal utility districts are governmental entities created to provide water services, while mobile home parks often have their own water distribution systems established for residents. Rural water supply corporations are non-profit entities aimed at providing water to rural areas, thus fulfilling the criteria for community water systems.

The distinction lies in the structure and purpose of the entities involved; private companies may operate water facilities but do so at a profit-driven level and may not always meet the regulatory criteria that define community water systems.