What process occurs at the boundary between the capillaries and the alveoli? A.
Nitrogen enters the alveoli, and oxygen enters the capillaries.
B.
Oxygen enters the alveoli, and carbon dioxide enters the capillaries.
C.
Oxygen enters the alveoli, and nitrogen enters the capillaries.
D.
Carbon dioxide enters the alveoli, and oxygen enters the capillaries.

D.  Carbon dioxide enters the alveoli, and oxygen enters the capillaries.

Explanation:

This describes the exchange of gases in the lungs. When blood from the rest of the body gets to the lungs through the capillaries, oxygen flows from the alveoli which are tiny air sacs in the lungs, into the blood in the capillaries.

Carbon dioxide from the blood brought to the lungs will then flow into the alveoli which will then expel it through the nose. This repeated process ensures that the body keeps getting oxygen and expelling carbon dioxide.

thermophiles, notice the prefix thermo.

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