Final answer:
The alveolar pressure during inspiration is less than the alveolar pressure during expiration because the lungs are at a negative pressure compared to the atmosphere during inspiration and at a positive pressure during expiration.
Step-by-step explanation:
Based on the provided key and the explanation of alveolar pressures during inspiration and expiration, we can determine the best answer for the comparison between alveolar pressure during inspiration (1) and expiration (2). During inspiration, the muscles expand the chest, and the diaphragm moves downward, creating a negative gauge pressure inside the lungs that is less than atmospheric pressure. This negative pressure is known as intra-alveolar pressure during inspiration. On the contrary, during expiration, the muscles relax, and the surface tension in the alveoli creates a positive pressure inside the lungs, which is greater than the atmospheric pressure, forcing air out.
Therefore, if we were to apply the provided key to the question, the answer would be: (a) the first item (alveolar pressure during inspiration) is less than the second item (alveolar pressure during expiration).