Question

external respiration refers to the exchange of oxygen and carbon dioxide between the:
a alveoli and bloodstream.
b outside air and cells of the body.
c bloodstream and cells.
d lungs and heart.

Explanation:

External respiration is the gas - exchange process where oxygen from inhaled air in the alveoli diffuses into the bloodstream and carbon dioxide from the bloodstream diffuses into the alveoli to be exhaled.

Answer:

A. alveoli and bloodstream.