**Core Concept**
Gonorrhea is a sexually transmitted infection caused by the bacterium *Neisseria gonorrhoeae*. Effective treatment requires antibiotics that can penetrate the mucosal secretions and target the bacteria at the site of infection.

**Why the Correct Answer is Right**
The recommended single-dose treatment for gonorrhea is ceftriaxone, a third-generation cephalosporin antibiotic. Ceftriaxone works by inhibiting cell wall synthesis in *N. gonorrhoeae*, ultimately leading to bacterial death. This mechanism is due to the antibiotic's ability to bind to penicillin-binding proteins (PBPs) on the bacterial cell wall, which are essential for cell wall synthesis.

**Why Each Wrong Option is Incorrect**
**Option A:** Azithromycin is used as an adjunct treatment for gonorrhea but is not sufficient as a single-dose treatment due to the emergence of resistance.
**Option B:** Fluoroquinolones, such as ciprofloxacin, were previously used to treat gonorrhea but are no longer recommended due to widespread resistance.
**Option C:** Metronidazole is an antibiotic effective against anaerobic bacteria and is not indicated for the treatment of gonorrhea.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the Centers for Disease Control and Prevention (CDC) recommend dual antibiotic therapy for gonorrhea treatment, including ceftriaxone and azithromycin, to address emerging resistance.

**Correct Answer: C. Ceftriaxone.**