Concept:Breathing is the process by which air moves between the outside environment and the respiratory organs of an animal.
Explanation:Vertebrates take in oxygen from the surroundings and release carbon dioxide to the surroundings.
This exchange of gases at the level of the respiratory organs is a physical process, not a chemical one.
Inhalation and expiration are simply the two phases of this process.
Respiration, on the other hand, is the cellular breakdown of food to release energy, which involves chemical reactions inside cells.
Since the question specifically talks about gas exchange between the environment and the respiratory organs, it points to the act of breathing.
Thus, the correct term is breathing, not inhalation alone, not expiration alone, and not respiration.
Answer:D. breathing