What is a function tested in cranial nerve VIII (vestibulocochlear nerve)?

Cranial nerve VIII, known as the vestibulocochlear nerve, has two primary functions: it is responsible for hearing (the cochlear part) and balance (the vestibular part). When testing this cranial nerve, assessments often focus on hearing acuity, which involves evaluating the ability to perceive sounds of various frequencies and intensities. This is typically conducted through audiometric tests or simple hearing assessments, such as whispering or tuning fork tests.

The other options relate to different cranial nerves. The ability to swallow involves cranial nerves IX (glossopharyngeal) and X (vagus). Voice quality is influenced by cranial nerve X (vagus) and is associated with the control of the vocal cords. Facial symmetry pertains to cranial nerve VII (facial), which deals with the muscles of facial expression. Thus, the testing of cranial nerve VIII is specifically aimed at assessing hearing acuity, confirming why this is the correct answer.