Final answer:
Nerve agents are the most deadly among the three types discussed, causing rapid and severe symptoms that can lead to death by asphyxiation or cardiac arrest within minutes of exposure.
Step-by-step explanation:
Among nerve agents, blood agents, and blister agents, nerve agents cause the most casualties. Nerve agents are a class of organic chemicals that act as acetylcholinesterase inhibitors, which disrupt the transmission of nerve impulses to organs, leading to symptoms such as pupil constriction, salivation, convulsions, and respiratory failure. Exposure can result in death by asphyxiation or cardiac arrest within minutes due to the loss of control over respiratory muscles. These substances can be absorbed through the skin or inhaled as they can vaporize into the air, hence full body suits and respirators are necessary for protection.
Blood agents also act through inhalation affecting the respiratory system severely, often resulting in suffocation, while blister agents cause severe skin, eye, and mucosal pain and damage. However, nerve agents are commonly understood to be the most lethal due to their rapid mechanism of action and the difficulty involved in immediate and effective treatment.