Final answer:
The intrapleural pressure equalized with the atmospheric pressure when the valve was opened, causing the lung to collapse instead of expand; thus, the lung did not become larger nor did airflows increase.
Step-by-step explanation:
When the valve to the left side of the bell jar was opened, the intrapleural pressure equalized with the atmospheric pressure. Under normal conditions, the intrapleural pressure is negative relative to both intra-alveolar and atmospheric pressures due to the outward pull of the thoracic wall being slightly greater than the inward pull of the lung's elasticity and surface tension of alveolar fluid. The opening of the valve would interrupt the negative pressure system, allowing air to enter the pleural cavity and causing the lung to collapse rather than expand, negating options (a) and (c). Thus, the lung would not become larger, and there would be no increase in airflows as a result of the valve opening.