**Core Concept**
A depolarising muscle relaxant works by inducing a persistent depolarisation of the muscle cell membrane, leading to muscle contraction followed by paralysis. This class of muscle relaxants activates nicotinic acetylcholine receptors at the neuromuscular junction.

**Why the Correct Answer is Right**
The correct answer is a depolarising muscle relaxant because it activates the nicotinic acetylcholine receptors at the neuromuscular junction, mimicking the action of acetylcholine. This results in an initial muscle contraction, followed by a persistent depolarisation and eventual paralysis. The depolarisation is due to the influx of sodium ions into the muscle cell, which cannot repolarise due to the continued activation of the nicotinic receptors.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because it is actually a non-depolarising muscle relaxant, which works by blocking the nicotinic acetylcholine receptors at the neuromuscular junction, preventing acetylcholine from binding.
* **Option B:** This is incorrect because it is a combination of a non-depolarising and a depolarising muscle relaxant, and its exact mechanism is not relevant to the question.
* **Option D:** This is incorrect because it is a neuromuscular blocking agent, but its exact mechanism is not relevant to the question.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that depolarising muscle relaxants can cause muscle fasciculations and initial muscle contractions before inducing paralysis. This is due to the initial activation of nicotinic acetylcholine receptors, leading to muscle contraction.

**Correct Answer:** C. Succinylcholine.