Which type of water system regularly supplies water to the same 25 people at least 6 months a year?

The correct choice is a Non-Transient Non-Community Water System because it specifically refers to water systems that regularly serve the same 25 or more people at least 6 months out of the year, but do not serve them as part of a residential community. This classification applies to facilities such as schools, factories, or hospitals where a stable group of people use the water over time, even if they don't live there.

In contrast, a Community Water System primarily serves a residential population, where the majority of users reside at the locations served by the system permanently. A Transient Water System supplies water to users who do not have a fixed residence and typically rotates between different users, such as those at a campground or rest stop. Lastly, a Public Well System could apply to various types of systems but does not fit the specific criteria regarding the same group of people using the system for at least 6 months per year.