Answer: Option D.
Damage to inner ear.
Step-by-step explanation:
Cochlea damage or inner damage causes permanent hearing loss.
It is the inner ear of Bob that is damaged because the inner ear is responsible for changing soundwaves to electrical waves because the inner ear make the brain to hear and understand sounds and therefore keeping balance . So damage to the inner ear causes hearing loss and inability to understand what is heard because the cochlea of the inner that change soundwaves to electrical signals or nerve impulses which allow the brain to hear and understand is damaged.
Some other symptoms of inner ear damage are;
Dizziness or spinning sensation (vertigo)
Nausea and vomiting.
Problems with balance or walking.
Hearing loss (or decrease in sound volume) in one ear.
Earache or ear pain.
Fever (sometimes)
Feeling of fullness in the ear.