Final answer:
The normal respiratory rate for an adult is between 12-20 RPM. It is controlled by the respiratory center in the brain and contributes to alveolar ventilation.
Step-by-step explanation:
The normal respiratory rate for an adult is between 12-20 RPM. The respiratory rate is the total number of breaths that occur each minute. It is controlled by the respiratory center located within the medulla oblongata in the brain, which responds primarily to changes in carbon dioxide, oxygen, and pH levels in the blood. The respiratory rate contributes to the alveolar ventilation, which prevents carbon dioxide buildup in the alveoli.