**Core Concept**
Nerve gases are a class of highly toxic organophosphorus compounds used in chemical warfare. They inhibit the enzyme acetylcholinesterase, leading to an accumulation of acetylcholine in the synapses and resulting in overstimulation of muscles and glands.

**Why the Correct Answer is Right**
Pyrolan is not a nerve gas, unlike the other options. The correct nerve gases in the list are Sarin (GB), Tabun (GA), and Soman (GD), which are all potent inhibitors of acetylcholinesterase. Pyrolan, on the other hand, is not classified as a nerve gas. It is possible that the question is testing the student's knowledge of chemical warfare agents.

**Why Each Wrong Option is Incorrect**
**Option A:** Sarin (GB) is a well-known nerve gas that inhibits acetylcholinesterase, leading to muscle weakness, paralysis, and respiratory failure.
**Option B:** Tabun (GA) is another potent nerve gas that works by inhibiting acetylcholinesterase, causing overstimulation of muscles and glands.
**Option C:** Soman (GD) is a highly toxic nerve gas that also inhibits acetylcholinesterase, leading to severe symptoms and death.

**Clinical Pearl / High-Yield Fact**
It is essential to note that nerve gases are highly toxic and can be fatal even with minimal exposure. Medical professionals should be aware of the symptoms and treatment of nerve gas poisoning, which include atropine administration and oximes to re-activate acetylcholinesterase.

**✓ Correct Answer: D. Pyrolan**