The correct option is B Intrapulmonary pressure < atmospheric pressure
A pressure gradient is required to guide the air movement into and out of the lungs. The air movement between the lungs and the atmosphere is carried by the pressure gradient created between them. Negative pressure in the lungs with respect to the atmosphere can result in the movement of atmospheric air into the lungs which is called inspiration. So, inspiration can only occur when intrapulmonary pressure is less than the atmospheric pressure.
In case of expiration, the intrapulmonary pressure is higher than the atmospheric pressure so that the alveolar air is released out. When intrapulmonary pressure equals atmospheric pressure, there is no air movement.