**Core Concept**
The basilar membrane is a critical structure in the cochlea of the inner ear responsible for sound processing. It is a flexible, tonotopic membrane that vibrates in response to sound waves, allowing for the detection of different frequencies.

**Why the Correct Answer is Right**
The basilar membrane is widest at the base and tapers to a point at the apex. As a result, the stiffness of the membrane decreases from the base to the apex. Higher frequency sounds cause the basilar membrane to vibrate more towards the base, whereas lower frequency sounds cause it to vibrate towards the apex. This phenomenon is known as the "tonotopic organization" of the cochlea. The location along the basilar membrane where the highest frequency sounds are detected is the region closest to the base, where the membrane is stiffest and can respond to the most rapid vibrations.

**Why Each Wrong Option is Incorrect**
**Option A:** The apical region of the basilar membrane is responsible for detecting lower frequency sounds, not higher frequency sounds.
**Option B:** The middle region of the basilar membrane is also responsible for detecting lower to mid-frequency sounds, but not the highest frequency sounds.
**Option C:** The basal end of the cochlea, which is the entrance to the scala tympani, is not the location where the highest frequency sounds are detected.

**Clinical Pearl / High-Yield Fact**
Remember that the tonotopic organization of the cochlea is a critical concept in understanding hearing and balance disorders. Damage to the basal end of the cochlea can result in high-frequency hearing loss, while damage to the apical end can result in low-frequency hearing loss.

**Correct Answer: C.**