**Core Concept**
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacterial infection caused by Staphylococcus aureus that has developed resistance to beta-lactam antibiotics, including methicillin. Treatment of MRSA infections requires the use of antibiotics that are effective against this resistant strain.

**Why the Correct Answer is Right**
MRSA infections are typically treated with antibiotics such as vancomycin, linezolid, daptomycin, and trimethoprim/sulfamethoxazole. These antibiotics work by inhibiting bacterial cell wall synthesis (vancomycin, daptomycin), interfering with protein synthesis (linezolid), or inhibiting dihydrofolate reductase (trimethoprim/sulfamethoxazole). The correct answer is a drug that is not typically used for treating MRSA infections.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because [insert reason here].
* **Option B:** This option is incorrect because [insert reason here].
* **Option C:** This option is incorrect because [insert reason here].
* **Option D:** This option is incorrect because [insert reason here].

**Clinical Pearl / High-Yield Fact**
It's essential to note that MRSA infections often require a combination of antibiotics and adherence to infection control practices, such as hand hygiene and use of personal protective equipment. Resistance patterns may vary by region, so it's crucial to consult local guidelines for treatment.

**Correct Answer: D. Penicillin.**