## **Core Concept**
The question targets the knowledge of scabies treatment, specifically ovicidal drugs. Scabies is a skin infestation caused by the mite *Sarcoptes scabiei*. Ovicidal drugs are those that kill the eggs of the scabies mite.

## **Why the Correct Answer is Right**
The correct answer, **C. Permethrin**, is an ovicidal drug effective against scabies. Permethrin works by killing the scabies mite and its eggs. It is a topical cream that is applied to the skin from the neck down in most cases. Permethrin is considered a first-line treatment for scabies due to its efficacy and safety profile.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Ivermectin is an oral medication used to treat scabies but is not primarily known for its ovicidal action. It works by affecting the nervous system of the mite.
- **Option B:** Lindane has ovicidal activity but is not the first choice due to potential neurotoxicity, especially in children and pregnant women.
- **Option D:** Sulfur is an ovicidal agent but is less commonly used nowadays due to its unpleasant smell and potential for skin irritation.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that permethrin cream is often considered the drug of choice for treating scabies, especially in children and pregnant women, due to its efficacy and safety profile. It's applied from the neck down and left on for 8-14 hours before being washed off.

## **Correct Answer:** C. Permethrin.