## Core Concept
Lichenification, also known as lichenisation, is a characteristic skin change that occurs in response to chronic scratching or rubbing. It involves thickening of the skin due to an increase in the number of cell layers. This process primarily affects the **stratum corneum** and the **epidermis** but is most notably associated with the epidermal layer.

## Why the Correct Answer is Right
The correct answer, **stratum corneum and epidermis (D)**, is right because lichenisation involves the thickening of the epidermis and hyperkeratosis (an increase in the thickness of the stratum corneum). This thickening is a result of the skin's response to repeated friction or scratching, leading to an increase in cell layers, particularly in the epidermis and the stratum corneum.

## Why Each Wrong Option is Incorrect
- **Option A:** Dermis - While the dermis can show changes in response to chronic inflammation or damage, lichenisation primarily involves changes in the epidermal layer rather than the dermal layer.
- **Option B:** Subcutaneous tissue - This layer is not directly involved in the process of lichenisation, which is more superficial.
- **Option C:** Epidermis - Although lichenisation does involve changes in the epidermis, specifying only the epidermis might be considered incomplete since the stratum corneum, a part of the epidermis, is also significantly involved.

## Clinical Pearl / High-Yield Fact
A key point to remember is that lichenisation often presents as thickened, hyperpigmented skin with increased skin markings, commonly seen in conditions like eczema or dermatitis where scratching is a prominent feature. Recognizing lichenisation can help in diagnosing and managing chronic skin conditions.

## Correct Answer: D. Epidermis.