Final answer:
In the lungs, expiration will occur if intrapleural pressure equals or exceeds atmospheric pressure, as this would prevent the lungs from expanding during inhalation and lead to the air flowing out of the lungs. The diaphragm's paralysis would prevent inhalation by not allowing the change in intrapleural pressure necessary for air to enter the lungs.
Step-by-step explanation:
If intrapleural pressure equals or increases above atmospheric pressure, expiration will occur in the lungs. This is because the intrapleural pressure will be higher than or equal to the outside atmospheric pressure, leading to a collapse of the lung or prevention of air inflow. During normal respiration, the intrapleural pressure is lower than atmospheric pressure during inhalation, which allows the lungs to expand as air rushes in to equalize the pressure. During expiration, the muscles relax, the volume of the thoracic cavity decreases, and the pressure inside the lungs becomes greater than the atmospheric pressure, causing air to flow out.
Paralysis of the diaphragm would prevent this pressure change, as the diaphragm's contraction powers the decrease in thoracic pressure that is necessary for inhalation. Hence, paralysis of the diaphragm would result in option b. It would prevent inhalation because the intrapleural pressure would not change.