Final answer:
The correct answer to the question is d) Oval Window. This membrane vibrates to conduct sound from the middle ear to the fluid in the cochlea of the inner ear.
Step-by-step explanation:
The membrane across the opening between the middle ear and the inner ear that conducts vibrations to the cochlea is called the oval window. The middle ear holds three small bones known as ossicles, which include the malleus, incus, and stapes. The last of these, the stapes, transmits the vibrations to the oval window. This thin membrane vibrates, causing the fluid inside the cochlea to move, initiating the process of converting mechanical vibrations into electrical signals that the brain can interpret as sound.