**Core Concept**
The question is testing the knowledge of neuromuscular blocking agents, specifically their onset of action. Neuromuscular blocking agents are a class of drugs that temporarily paralyze muscles by blocking the transmission of nerve impulses at the neuromuscular junction.

**Why the Correct Answer is Right**
Succinylcholine is a depolarizing neuromuscular blocking agent with a rapid onset of action, typically less than 1 minute, but can be as fast as 30 seconds. It works by mimicking the action of acetylcholine at the neuromuscular junction, causing an initial depolarization of the muscle fibers. This leads to a rapid onset of muscle paralysis.

**Why Each Wrong Option is Incorrect**
**Option A:** Rocuronium has an onset of action of approximately 1-2 minutes, making it slower than succinylcholine.
**Option B:** Vecuronium has a slower onset of action, typically around 2-3 minutes, making it even slower than rocuronium.
**Option C:** Atracurium has a variable onset of action, but it is typically around 2-3 minutes, making it slower than succinylcholine.

**Clinical Pearl / High-Yield Fact**
Succinylcholine is often used in emergency situations where rapid muscle paralysis is required, such as in cases of laryngospasm or in patients who are difficult to intubate.

**Correct Answer:** C. Succinylcholine