**Core Concept:** The respiratory muscles play a crucial role in maintaining lung inflation and preventing lung collapse during exhalation. The diaphragm is the primary muscle involved in respiration, while the intercostal muscles help to expand the ribcage. When these muscles are relaxed, the lungs are in a state of decreased inflation, which leads to increased intra-thoracic pressure and may result in lung collapse (atelectasis) if not counteracted by other forces.

**Why the Correct Answer is Right:** In the absence of respiratory muscle contraction, the lungs would experience a decrease in inflation due to the absence of the forces generated by the diaphragm and intercostal muscles. This leads to an increase in intra-thoracic pressure, which in turn causes the pleural pressure to decrease, promoting lung collapse (atelectasis) if not counteracted by other forces, such as the elastic recoil of the lung parenchyma or the pericardium.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because when the respiratory muscles are relaxed, lung inflation is decreased due to the absence of the forces generated by the diaphragm and intercostal muscles.
B. This option is incorrect since the relaxation of respiratory muscles does not cause lung inflation to increase. Instead, it leads to decreased inflation as explained above.
C. This option is incorrect because when respiratory muscles are relaxed, lung inflation is decreased, not increased, due to the absence of the forces generated by the diaphragm and intercostal muscles.
D. This option is incorrect as relaxation of respiratory muscles does not result in lung inflation being "greater" but, as mentioned, leads to decreased inflation due to the absence of the forces generated by the diaphragm and intercostal muscles.

**Clinical Pearl:** Understanding the role of respiratory muscles in maintaining lung inflation is essential for recognizing and managing respiratory distress syndromes, such as those seen in patients with neuromuscular disorders or during general anesthesia when patients are paralyzed. Atelectasis (lung collapse) may occur if the forces generated by the respiratory muscles are not counteracted by other forces, such as elastic recoil of the lung parenchyma or the pericardium.