What would happen to the alveoli during expiration without pulmonary surfactant?

1. Water lining the alveoli creates surface tension that tends to inhibit their expansion. 2. Pulmonary surfactant secreted by type II alveolar cells mixes with that water and reduces the surface tension. 3. Remove the surfactant and the surface tension is unopposed. 4. The alveoli would then collapse during expiration, so the second option is correct. 5. Over-inflation is the opposite failure and is guarded against by the inflation reflex, not by surfactant. 6. Pleural fluid stays in the pleural cavity outside the lung tissue, so the third option moves fluid to the wrong compartment. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 22 "The Respiratory System", section 22.3 The Process of Breathing_