Which of the following is an example of a nerve agent?

The correct choice, Sarin, is classified as a nerve agent because it specifically targets the nervous system, leading to severe physiological effects that can result in loss of bodily functions and even death. Nerve agents work by inhibiting the enzyme acetylcholinesterase, which is crucial for breaking down the neurotransmitter acetylcholine. When acetylcholine builds up in the synapses due to the inhibition, it causes continuous stimulation of the nerves, leading to symptoms such as muscle twitching, paralysis, and respiratory failure.

In contrast, the other substances listed are chemical agents but do not belong to the nerve agent category. Hydrogen cyanide is a blood agent that disrupts cellular respiration. Distilled mustard, also known as mustard gas, is classified as a blistering agent that causes severe skin and respiratory tract damage. Phosgene is a choking agent that primarily affects the lungs. Understanding these classifications helps in recognizing the specific threats and mechanisms of action associated with different chemical agents.