**Core Concept**
Malignant hyperthermia (MH) is a life-threatening medical emergency triggered by certain anesthetic agents, particularly volatile anesthetics and succinylcholine, in susceptible individuals. This condition is characterized by an uncontrolled increase in body temperature, muscle rigidity, and autonomic dysfunction.

**Why the Correct Answer is Right**
Succinylcholine, a depolarizing neuromuscular blocker, is contraindicated in patients with a history of malignant hyperthermia. This is because succinylcholine can trigger a malignant hyperthermic crisis by releasing calcium ions from the sarcoplasmic reticulum, leading to an uncontrolled muscle contraction and subsequent heat production. The use of succinylcholine in these patients can be fatal.

**Why Each Wrong Option is Incorrect**
* **Option A:** Rocuronium, a non-depolarizing neuromuscular blocker, is not contraindicated in patients with malignant hyperthermia. It is a safer alternative for neuromuscular blockade in these patients.
* **Option B:** Fentanyl, a synthetic opioid anesthetic, is not contraindicated in patients with malignant hyperthermia. In fact, opioids like fentanyl are often used as part of the treatment protocol for malignant hyperthermia.
* **Option D:** Vecuronium, another non-depolarizing neuromuscular blocker, is not contraindicated in patients with malignant hyperthermia. Like rocuronium, vecuronium is a safer alternative for neuromuscular blockade in these patients.

**Clinical Pearl / High-Yield Fact**
In patients with a history of malignant hyperthermia, it is essential to use non-depolarizing neuromuscular blockers like rocuronium or vecuronium instead of succinylcholine. This can help prevent a malignant hyperthermic crisis during anesthesia.

**Correct Answer:**
C. Succinylcholine