Which agents can damage the membranes of the lungs causing coughing and choking?

Choking agents are chemicals specifically designed to damage lung membranes, resulting in severe respiratory distress, coughing, and choking. These agents primarily target the respiratory system, leading to fluid buildup in the lungs, which can cause a sensation of suffocation and create breathing difficulties.

While irritants can also affect the respiratory system and lead to coughing, they generally cause discomfort without the specific targeting or severe effects characteristic of choking agents. Blood agents are toxic substances that interfere with the body's ability to utilize oxygen but do not primarily damage lung membranes. Vesicants are chemicals that cause blisters on the skin and mucous membranes, and while they can cause respiratory issues when inhaled, their primary mode of harm is not through the direct damage of lung membranes in the way choking agents do.

Overall, choking agents are distinct in their mechanism of action and outcomes, making them the correct answer for this question.