Final answer:
The average adult respiratory rate per minute under non-exertion conditions falls between 12 and 18 breaths. Option B) 18 breaths per minute is within this normal range and is correct. Respiratory rates significantly higher or lower can indicate health issues.
Step-by-step explanation:
The average adult ranges for respiratory rate per minute fall between 12 and 18 breaths when a person is not exerting themselves. Therefore, the answer to the question of which respiratory rate per minute falls within the average adult range is B) 18 breaths per minute. This number is closer to the average rate compared to the other options, as very slow breathing rates like 8 breaths per minute and faster rates such as 28 or 38 breaths per minute are typically not considered normal for resting adults. The respiratory center within the medulla oblongata in the brain tightly regulates the respiratory rate based on the body's needs, particularly responding to changes in carbon dioxide, oxygen, and pH levels in the blood. Knowing the healthy range of respiratory rates can be an important indicator of disease, as deviations from the normal range may signal health issues.