Final answer:
The base of the cochlea refers to the thin and rigid region of the basilar membrane that is tuned to high frequencies. The provided options do not include the correct term for the base of the cochlea. Options such as the apex, middle ear, tympanic membrane, and round window refer to different anatomical parts of the ear.
Step-by-step explanation:
The base of the cochlea, specifically the region of the basilar membrane located at this base, is known for being thin and rigid. This area is where high frequencies are best detected and heard because it is tuned to respond to high-pitch sounds. As a person ages, this area of the cochlea can become damaged, often leading to hearing loss for high-pitched sounds. Now, regarding the choices provided in the question, the correct term for the base of the cochlea is not provided. The apex refers to the opposite end of the cochlea where it is smallest and where low frequencies are heard. The middle ear is an anatomical region that includes structures such as the ossicles but is not part of the cochlea. The tympanic membrane, also known as the eardrum, is where the auditory process begins as it vibrates upon sound waves hitting it. Lastly, the round window is another structure, not the base of the cochlea, but it allows pressure waves to dissipate within the cochlear fluid.