Under what conditions does an artesian well occur?

An artesian well occurs under specific geological conditions that involve the presence of a confined aquifer. A confined aquifer is characterized by water being trapped between layers of impermeable rock or sediment, known as aquitards. This confinement creates pressure within the aquifer, and when a well is drilled into it, the built-up pressure forces the water to rise to the surface without the need for pumping.

In this scenario, water must be in an inclined aquifer, which contributes to the pressure gradient required for the water to flow naturally to the surface. This is why the correct option emphasizes the necessity of both a confined aquifer and the presence of aquitards. Other options do not satisfy the criteria required for the formation of an artesian well; for instance, an open aquifer cannot maintain the necessary pressure for an artesian well to function, nor are the geographical proximity to a river and high evaporation rates relevant to the mechanism of artesian wells.