Answer:D
Explanation: The pulmonary air sacs of birds only permit a unidirectional flow of air through the lungs. Unidirectional flow means that air is inhale and exhale through one trachea alternatively. This means the bird lungs only receive largely fresh air which has a high oxygen content during inhalation and do not receive fresh during exhalation. While air flow bidirectional in mammals.
Answer:
I would say either oil or eggs?
Explanation:
Only rely on this answer if you're desperate! I don't know...
Answer:
that would be C, seafloor spreading occurs!
Explanation:
