A.I. Explanation:

Option 1: "It transmits vibrations to the auditory nerve."

Explanation: This option is incorrect because the pinna does not transmit vibrations to the auditory nerve. Instead, the pinna's role is to collect sound waves and direct them into the auditory canal. The transmission of vibrations to the auditory nerve occurs later in the process, after the sound waves have been converted into nerve impulses in the inner ear.

Option 2: "It vibrates in response to sound waves."

Explanation: This option is incorrect as the pinna itself does not vibrate in response to sound waves. The eardrum is the part that vibrates when sound waves hit it. The pinna's function is to capture sound waves and funnel them into the auditory canal, not to vibrate.

Option 3: "It equalises air pressure in the middle ear."

Explanation: This option is incorrect because the pinna does not play a role in equalising air pressure in the middle ear. The Eustachian tube is responsible for equalising air pressure. The pinna's primary function is to receive sound waves and direct them into the auditory canal.

Option 4: "It receives sound waves and directs them into the auditory canal."

Explanation: This option is correct as it accurately describes the role of the pinna in the hearing process. The text states that the pinna of the outer ear receives sound waves, which is the first step in the auditory process. This aligns with the overall theme of how sound is processed through the ear.