Which of the following is a type of nerve agent?

VX is a type of nerve agent known for its lethal toxicity and mechanism of action. Nerve agents are a specific class of chemical warfare agents that disrupt the normal functioning of the nervous system by inhibiting acetylcholinesterase, an enzyme essential for breaking down the neurotransmitter acetylcholine. This inhibition leads to an accumulation of acetylcholine in synapses, resulting in overstimulation of muscles, respiratory failure, and potentially death due to the seizure of bodily functions.

VX, in particular, is an organophosphorus compound that is colorless, odorless, and considered one of the most toxic nerve agents. It was developed for military use and is classified as a weapon of mass destruction.

The other substances listed, while hazardous, fall under different categories. Mustard gas is classified as a blister agent and primarily affects the skin and respiratory system, Chlorine is a choking agent that can cause severe respiratory damage but does not interfere with the nervous system's functioning in the same way nerve agents do, and Carbon monoxide is a colorless, odorless gas that affects the body's ability to transport oxygen, leading to poisoning through hypoxia rather than a direct attack on the nervous system.