**Core Concept**
Nasal intubation is a technique used to place an endotracheal tube through the nasal passage into the trachea. However, it is not suitable for all patients due to specific anatomical and physiological limitations. The primary concern is the risk of complications arising from the nasal passage's unique characteristics.

**Why the Correct Answer is Right**
The correct answer is related to the anatomical structure of the nasal passage, specifically the nasal septum. A deviated nasal septum can lead to difficulty in passing the endotracheal tube through the nasal passage, increasing the risk of complications such as bleeding, nasal trauma, and airway obstruction. **Option C: Deviated nasal septum** is the correct answer because it poses a significant risk to the success and safety of nasal intubation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Septal perforation. While a septal perforation can increase the risk of complications during nasal intubation, it is not a contraindication. The presence of a perforation may require additional precautions, but it does not entirely preclude nasal intubation.
* **Option B:** Epistaxis (nosebleed). Epistaxis can be a complication of nasal intubation, but it is not a contraindication. In fact, nasal intubation can sometimes be used to manage severe epistaxis by securing the airway and allowing for better control of bleeding.
* **Option D:** Nasal polyps. Nasal polyps can cause difficulty in passing the endotracheal tube, but they are not a contraindication for nasal intubation. In some cases, nasal intubation may be possible with careful technique and planning.

**Clinical Pearl / High-Yield Fact**
When considering nasal intubation, it is essential to assess the patient's nasal anatomy, including the presence of a deviated septum or nasal polyps. A thorough examination and discussion with the patient can help determine the best approach for airway management. **Always consider alternative airway management strategies when nasal intubation is contraindicated or difficult.**

**Correct Answer: C. Deviated nasal septum**