The outer ear channels sound waves down the external to the a tight membrane that vibrates in response to sound waves.
a. auditory canal, oval window
b. pinna, eardrum
c. auditory canal, eardrum
d. pinna, cochlea

The outer ear channels sound waves down the external Auditory Canal to the Eardrum ,a tight membrane that vibrates in response to sound waves.

The external auditory canal acted as some sort of transmitter that move the  sound into a funnel that ended up in the ear drum. After it hits eardrum, it would create a vibration that  that sends message to the brain. The brain then would decipher it into the sound that we usually hear everyday.

C: Auditory Canal, Eardrum

Explanation: