**Core Concept**
Vancomycin is a glycopeptide antibiotic used to treat severe bacterial infections, including Clostridioides difficile (C. difficile) pseudomembranous colitis. The unique aspect of vancomycin in this context is that it is administered orally, despite being a drug that is typically administered parenterally.

**Why the Correct Answer is Right**
The oral administration of vancomycin in C. difficile pseudomembranous colitis is a direct result of the drug's mechanism of action. Vancomycin works by inhibiting cell wall synthesis in bacteria, ultimately leading to bacterial death. However, to be effective in treating C. difficile infections in the colon, vancomycin must be able to reach the site of infection in sufficient concentrations. Oral administration allows the drug to come into contact with the C. difficile bacteria in the colon, where it can exert its antibacterial effects. The drug is not absorbed from the gastrointestinal tract, which is ideal for this specific application.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided. Please ensure all options are listed for accurate analysis.
**Option B:** This option is not provided. Please ensure all options are listed for accurate analysis.
**Option C:** This option is not provided. Please ensure all options are listed for accurate analysis.
**Option D:** This option is not provided. Please ensure all options are listed for accurate analysis.

**Clinical Pearl / High-Yield Fact**
The oral route of administration of vancomycin in C. difficile pseudomembranous colitis is a classic example of a pharmacological approach that takes advantage of the drug's pharmacokinetic properties to achieve a specific therapeutic effect. This approach highlights the importance of understanding the drug's mechanism of action and how it can be optimized to achieve the best possible outcomes in clinical practice.

**Correct Answer:** C. Oral.