Which of the following is a key component of the respiratory system?

The alveoli are indeed a key component of the respiratory system because they are the tiny air sacs located at the end of the bronchial tubes in the lungs. Their primary function is to facilitate gas exchange, allowing oxygen to enter the bloodstream while carbon dioxide is expelled from the blood. This process is crucial for maintaining the body's oxygen levels and removing waste gases, which is vital for overall health.

In terms of the other options, while the diaphragm does play a significant role in respiration by aiding in the expansion and contraction of the lungs, it is primarily a muscle that supports the respiratory process rather than being a structural component of the respiratory system itself. The kidneys are part of the urinary system and are involved in filtration and regulation of body fluids, while the liver is part of the digestive system and has roles in metabolism and detoxification, neither of which pertains to the core functions of the respiratory system.