The correct answer is option 4, Artesian well. While option 1, Ordinary well, refers to a traditional well where a bucket or a pump is used to draw water, option 2, Tube well, refers to a well that is drilled into the ground using a long tube to access water from underground aquifers. Option 3, Deep tube well, is similar to a tube well but implies that the well is drilled deeper to access water from deeper aquifers.

An Artesian well, on the other hand, is a type of well that occurs when underground water is confined under pressure between layers of impermeable rock or clay. When a bored well is drilled into these layers, the hydraulic pressure forces the water up to the surface without the need for a pump. Artesian wells are known for their ability to naturally flow and supply water without any mechanical assistance.