Which window is located at the footplate of the stapes?

The oval window is the correct answer because it is the membrane-covered opening that is located at the footplate of the stapes, one of the three tiny bones in the middle ear known as the ossicles. When sound vibrations are transmitted through the ear and reach the stapes, its footplate presses against the oval window, initiating the process of converting these vibrations into fluid waves within the cochlea of the inner ear. This vital connection is necessary for the sensation of hearing to occur, as it allows the mechanical energy from the middle ear to influence the fluid dynamics in the inner ear.

In contrast, the round window serves a different purpose; it acts as a pressure release valve for the fluid waves created by the movements of the oval window. The Eustachian tube is responsible for equalizing pressure in the middle ear and does not have a direct relationship with the footplate of the stapes. The term "malleus window" is not a recognized anatomical structure in the context of the middle or inner ear. Thus, the oval window is specifically identified for its role and location, making it essential for normal auditory function.