**Core Concept**
Functional Endoscopic Sinus Surgery (FESS) is a minimally invasive surgical technique used to treat sinusitis and other sinus-related disorders. It involves the use of endoscopic instruments to remove blockages and restore normal sinus function.

**Why the Correct Answer is Right**
FESS is a type of surgical intervention that allows for the precise removal of diseased tissue and bone while preserving surrounding structures. The procedure is typically performed under general anesthesia and involves the use of a nasal endoscope to visualize the sinuses. During FESS, the surgeon can remove polyps, bone, and other obstructions that are blocking the sinuses, thereby restoring normal airflow and drainage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the procedure of FESS.
**Option B:** This option is incorrect because it is a different type of surgical procedure altogether.
**Option C:** This option is incorrect because it is not a recognized abbreviation for a surgical procedure.

**Clinical Pearl / High-Yield Fact**
FESS is often used to treat chronic sinusitis, which is a common condition characterized by persistent inflammation and infection of the sinuses. It is essential for clinicians to recognize the signs and symptoms of chronic sinusitis and to refer patients for FESS when appropriate.

**Correct Answer:** C. Functional Endoscopic Sinus Surgery