It is the last choice because their similar bone structures suggest they once had a common ancestor, which is why they are all mammals.
20. Cell Membrane 19. Mitochondria 18.<span> Osmosis</span>
Answer:
tympanic cavity .. The primary function of the tympanic cavity is to offset the decrease in acoustic energy that would occur if the low impedance ear canal air directly contacted the high-impedance cochlear fluid.
Explanation:
