What type of agent causes pulmonary edema?

The correct response identifies choking agents as the type that causes pulmonary edema. Choking agents, such as chlorine and phosgene, damage the lung tissues and can lead to edema, which is the accumulation of fluid in the lungs. This condition results in difficulty breathing and can be life-threatening, as it hampers the exchange of oxygen and carbon dioxide in the body.

Choking agents are designed to affect the respiratory system, directly impacting lung function and causing inflammation and fluid buildup. In contrast, biological agents are primarily meant to cause infections or diseases, nerve agents disrupt the nervous system, and blood agents affect the blood's ability to transport oxygen, none of which directly induce pulmonary edema in the same manner as choking agents. Understanding the specific effects of these agents highlights the importance of identifying and responding to chemical threats in medical and military situations.