[Review of the Respiratory System]
18. What conditions are necessary for air to be exhaled from the lungs?

A) Air pressure in the alveoli must become greater than the air pressure in the mouth.

B) Air pressure in the alveoli must become lower than the air pressure in the mouth.

C) Air pressure in the alveoli must become the same as the air pressure in the mouth.

D) There is no change in the air pressure of the alveoli or the mouth.

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Slichter