Final answer:
As we age, the number of hair cells in the cochlea decreases, which can lead to hearing loss and difficulties perceiving certain frequencies of sound.
Step-by-step explanation:
In the cochlea, which is part of the inner ear, there are hair cells responsible for converting sound vibrations into electrical signals that can be understood by the brain. As we age, these hair cells tend to decrease in number. This reduction in the number of hair cells can lead to hearing loss and difficulties in perceiving certain frequencies of sound.
Hair cells at the base of the cochlea respond best to high-frequency sounds, while those near the apex respond best to low-frequency sounds. The sensitivity of these hair cells allows for the detection of different frequencies of sound.
Therefore, the correct answer is c) They decrease.