**Core Concept**
Nodulocystic acne is a severe form of acne characterized by large, painful cysts and nodules on the skin. It is caused by a combination of factors, including excess oil production, bacterial growth, and inflammation. The goal of treatment is to reduce inflammation, prevent scarring, and improve the appearance of the skin.

**Why the Correct Answer is Right**
Treatment of nodulocystic acne often involves a combination of topical and systemic therapies. **Option C**, Isotretinoin, is a systemic retinoid that has been shown to be highly effective in reducing inflammation and preventing scarring. It works by decreasing the production of sebum, reducing bacterial growth, and inhibiting inflammation. Isotretinoin is often used as a last resort due to its potential side effects, but it is highly effective in treating severe cases of acne.

**Why Each Wrong Option is Incorrect**
* **Option A:** Benzoyl peroxide is a topical antibiotic that can help reduce bacterial growth and inflammation, but it is not effective in treating severe cases of nodulocystic acne.
* **Option B:** Sulfonamides are a class of antibiotics that can help reduce bacterial growth, but they are not effective in treating the underlying inflammation and scarring associated with nodulocystic acne.
* **Option D:** Steroids can be used to reduce inflammation in the short term, but they can also exacerbate acne in the long term and are not a suitable treatment for nodulocystic acne.

**Clinical Pearl / High-Yield Fact**
Isotretinoin is a teratogenic medication, meaning it can cause birth defects if taken during pregnancy. Women of childbearing age must use two forms of contraception while taking isotretinoin to prevent pregnancy.

**Correct Answer:** C. Isotretinoin.