Which of the following is NOT a type of well?

The term "dropped" is not recognized as a type of well in the context of plumbing and water supply systems. Wells are typically categorized based on their construction, depth, and water source. Artesian wells, for example, tap into confined aquifers under pressure, allowing water to flow naturally to the surface without the need for pumping. Shallow wells usually reach groundwater at relatively short depths and are more susceptible to pollution, while deep wells extend farther down to extract water from deeper aquifers, often providing cleaner supplies. Since "dropped" does not fit into these established categories, it is correctly identified as the option that does not represent a legitimate type of well.