**Core Concept**
Depolarizing muscle relaxants are a class of drugs that induce muscle relaxation by depolarizing the muscle cell membrane, leading to muscle contraction followed by prolonged relaxation. This class of drugs acts on the nicotinic acetylcholine receptors, specifically the N1 subtype, at the neuromuscular junction.

**Why the Correct Answer is Right**
The correct answer, Suxamethonium (Succinylcholine), is a depolarizing muscle relaxant that acts by mimicking the action of acetylcholine at the neuromuscular junction. It binds to nicotinic acetylcholine receptors, inducing a prolonged depolarization of the muscle cell membrane, which leads to muscle contraction followed by prolonged relaxation. This depolarization is due to the opening of sodium channels, allowing an influx of sodium ions, which triggers muscle contraction.

**Why Each Wrong Option is Incorrect**
* **Option A:** Rocuronium is a non-depolarizing muscle relaxant that competes with acetylcholine for binding to nicotinic acetylcholine receptors, preventing depolarization and muscle contraction.
* **Option B:** Vecuronium is also a non-depolarizing muscle relaxant that acts similarly to Rocuronium, preventing depolarization and muscle contraction.
* **Option D:** Atracurium is a non-depolarizing muscle relaxant that undergoes Hofmann elimination, a chemical process that inactivates the drug, leading to muscle relaxation.

**Clinical Pearl / High-Yield Fact**
Suxamethonium (Succinylcholine) can cause a rise in serum potassium levels due to the depolarization of muscle cells, which can be life-threatening in patients with certain cardiac conditions. It is essential to monitor patients receiving suxamethonium closely for signs of hyperkalemia.

**Correct Answer: C. Suxamethonium (Succinylcholine)**