Arteries:.

Choice A rationale:

A pneumothorax, or collapsed lung, occurs when air leaks into the space between the lung and chest wall. This is not directly caused by pressure in the lungs dropping lower than atmospheric pressure.

Choice B rationale:

Bronchioles constricting could lead to respiratory distress, but this is not a direct result of the pressure in the lungs dropping lower than atmospheric pressure.

Choice C rationale:

When the pressure within the lungs drops lower than atmospheric pressure, air flows into the lungs. This is a fundamental principle of respiration.

Choice D rationale:

Air flows out of the lungs when the pressure within the lungs rises above atmospheric pressure, not when it drops.

Choice A rationale:

While the spleen is the body’s largest lymphatic organ, this statement does not encompass all of its functions.

Choice B rationale:

The spleen does contribute to the production of white blood cells, but this is not its only function.

Choice C rationale:

The spleen does play a role in immunity, but it has other functions as well.

Choice D rationale:

This choice accurately describes the multiple functions of the spleen, including immunity, destruction of old red blood cells, blood storage, and hematopoiesis.