**Core Concept**
Toxic epidermal necrolysis (TEN) is a severe cutaneous adverse reaction characterized by widespread skin necrosis and detachment, often triggered by medications. The extent of skin involvement is a critical factor in determining the severity and prognosis of TEN.

**Why the Correct Answer is Right**
The correct answer is D. > 30% because skin involvement in TEN typically exceeds 30% of the body surface area (BSA). This level of skin detachment indicates a high risk of morbidity and mortality. In TEN, the epidermis and dermis undergo necrosis, leading to widespread skin sloughing and fluid loss. The severity of skin involvement correlates with the severity of systemic inflammation and the risk of complications, such as sepsis and multiorgan failure.

**Why Each Wrong Option is Incorrect**
**Option A:** Skin involvement of 30%