**Core Concept**
The question tests knowledge of pharmacology, specifically **muscle relaxants** and their properties, including allergy considerations. **Succinylcholine** is a depolarizing muscle relaxant, and its allergy necessitates the use of a non-depolarizing alternative.

**Why the Correct Answer is Right**
Given the allergy to **succinylcholine**, a non-depolarizing muscle relaxant should be chosen to avoid cross-reactivity and ensure patient safety. **Rocuronium** is often considered due to its rapid onset, which is crucial for facilitating endotracheal intubation, similar to **succinylcholine**.

**Why Each Wrong Option is Incorrect**
**Option A:** May not be the best choice due to its side effects or slower onset compared to other alternatives.
**Option B:** Could be incorrect due to its pharmacokinetic profile not matching the needs of rapid sequence intubation as closely as the correct answer.
**Option D:** Might be wrong because it doesn't offer the same rapid onset as the preferred agent in this context.

**Clinical Pearl / High-Yield Fact**
In patients allergic to **succinylcholine**, choosing a non-depolarizing agent like **rocuronium** can be life-saving, especially in emergency situations requiring rapid sequence intubation.

**Correct Answer:** D. Rocuronium.