Answer:
it is A I tried to work it out my best have a nice day God bless you
A fern is a vascular plant.
Answer:
If oxygen supply is depleted the muscle cells will respire anaerobically and release lactic acid and energy.
The accumulation of lactic acid , results in a pain in the muscles of the athlete.
Explanation:
If the inner lining of the air sacs neither thin nor highly vascularized, then it can be inferred that AIR SACS ARE CANNOT BE THE SITES OF GASEOUS EXCHANGE BETWEEN AIR AND BLOOD. Air sacs are generally lined with mucus and surrounded with blood capillaries.
In case of birds, air sacs play an important role in respiratory system.
