**Core Concept**
The question pertains to the treatment of scabies, a skin infestation caused by the mite Sarcoptes scabiei. Ovicidal drugs are specifically designed to kill the eggs of the mite, thereby preventing re-infestation and the prolonged treatment period associated with scabies.

**Why the Correct Answer is Right**
Permethrin is a topical ovicidal agent that is widely used in the treatment of scabies. It belongs to the pyrethroid class of insecticides and works by disrupting the nervous system of the mite, ultimately leading to its death. Permethrin is particularly effective against the eggs of the mite, which are resistant to other treatments. The use of permethrin cream 5% for 8-12 hours is a recommended treatment regimen for scabies, as it ensures the killing of the eggs while minimizing the risk of resistance.

**Why Each Wrong Option is Incorrect**
**Option A:** BHC (Benzene Hexachloride) is an older insecticide that was used to treat scabies, but it has largely been replaced by more effective and safer alternatives like permethrin. BHC has been linked to various health concerns and is no longer recommended for the treatment of scabies.
**Option B:** DDT (Dichlorodiphenyltrichloroethane) is a well-known insecticide that has been used to control a wide range of pests, including mosquitoes and flies. However, its use in the treatment of scabies is not recommended due to its potential toxicity and resistance concerns.
**Option C:** HHC (Hexachlorocyclohexane) is a chemical compound that has been used as an insecticide, but it is not commonly associated with the treatment of scabies. Its use has been largely discontinued due to environmental and health concerns.

**Clinical Pearl / High-Yield Fact**
When treating scabies, it is essential to cover all areas of the body, including the scalp, face, and genital areas, to ensure complete eradication of the mite. Permethrin cream 5% should be applied from the neck down and washed off after 8-12 hours.

**✓ Correct Answer: D. Permethrin**