**Core Concept**
The nasal mucosa is a complex structure composed of epithelial cells, blood vessels, and mucous glands, and its blood supply is essential for maintaining its functions, including filtration of inspired air, secretion of mucous, and protection against pathogens.

**Why the Correct Answer is Right**
The nasal mucosa is primarily supplied by the sphenopalatine artery, which is a terminal branch of the maxillary artery. This artery arises from the first part of the maxillary artery and enters the nasal cavity through the sphenopalatine foramen. The sphenopalatine artery then divides into several smaller branches that supply the nasal mucosa, including the superior, middle, and inferior nasal conchae. The blood supply to the nasal mucosa is crucial for its function and is often affected in conditions such as nasal congestion and epistaxis.

**Why Each Wrong Option is Incorrect**
* **Option A:** The external carotid artery is not directly responsible for the blood supply to the nasal mucosa, although its branches, including the maxillary artery, contribute to it indirectly.
* **Option B:** The internal carotid artery primarily supplies the brain and does not directly contribute to the blood supply of the nasal mucosa.
* **Option C:** The facial artery does contribute to the blood supply of the nasal mucosa, but it is not the primary source of blood supply.

**Clinical Pearl / High-Yield Fact**
The sphenopalatine artery is often involved in epistaxis (nosebleeds), and its ligation is a common procedure performed to control severe nasal bleeding.

**Correct Answer: C. The sphenopalatine artery.**