The area-reduction principle in the middle ear explains:

• A. It concentrates force from a large surface to a small surface, increasing pressure on cochlear fluids.
• B. It decreases pressure transmitted to the cochlear fluids.
• C. It balances the tympanic membrane with the round window.
• D. It prevents ossicle fatigue.

Answer: (D)

The area-reduction principle is about impedance matching in the middle ear: the tympanic membrane has a much larger surface area than the oval window, so sound pushes on a large surface and the force is directed into a much smaller area. This concentrates the force and increases the pressure that reaches the cochlear fluids, making it easier to move the fluid and transfer energy into the inner ear. That increased pressure at the oval window is the key idea, not a decrease in pressure. So the best statement is that it concentrates force from a large surface to a small surface, increasing pressure on cochlear fluids. The other ideas don’t fit this mechanism: it doesn’t describe decreased pressure, it doesn’t relate to balancing the tympanic membrane with the round window, and it isn’t about preventing ossicle fatigue.