Question

question 19 in external respiration: a oxygen is inhaled into the lungs and absorbed into the bloodstream b oxygen and carbon dioxide are exchanged c oxygen leaves the bloodstream d carbon dioxide enters the bloodstream

Explanation:

External respiration is the gas exchange between the alveoli of the lungs and the blood. In this process, oxygen from the alveoli diffuses into the bloodstream, and carbon dioxide from the blood diffuses into the alveoli to be exhaled. Option A is incorrect because inhalation is part of ventilation, not just external respiration's gas exchange. Option C is wrong as oxygen enters, not leaves, the bloodstream. Option D is incorrect as carbon dioxide leaves the bloodstream. Option B correctly describes the exchange of oxygen (into blood) and carbon dioxide (out of blood) in external respiration.

Answer:

B. oxygen and carbon dioxide are exchanged