**Core Concept**
Pseudomembranous enterocolitis, also known as Clostridioides difficile (C. diff) infection, is a bacterial infection caused by the overgrowth of C. difficile in the gut. The treatment of choice for this infection involves eradicating the bacteria and restoring the balance of the gut microbiome.

**Why the Correct Answer is Right**
Vancomycin is a lipoglycopeptide antibiotic that is effective against C. difficile. It works by inhibiting cell wall synthesis in bacteria, ultimately leading to their death. Vancomycin is not absorbed from the gastrointestinal tract, allowing it to act locally on the bacteria in the gut. This makes it an ideal treatment for C. difficile infection, as it can effectively reduce the bacterial load without being absorbed into the bloodstream.

**Why Each Wrong Option is Incorrect**
**Option A:** Metronidazole is an antibiotic that is sometimes used to treat C. difficile infection, but it is not the preferred treatment due to concerns about resistance and lower efficacy compared to vancomycin.
**Option B:** Ciprofloxacin is a fluoroquinolone antibiotic that can actually contribute to the development of C. difficile infection by disrupting the balance of the gut microbiome.
**Option C:** Amoxicillin is a beta-lactam antibiotic that is not effective against C. difficile.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the treatment of C. difficile infection involves more than just antibiotics. Fecal microbiota transplantation (FMT) has emerged as a promising treatment option, and it's crucial to consider this in recurrent or severe cases.

**Correct Answer:** C. Vancomycin.