**Core Concept**
The epidermis is the outermost layer of the skin, composed of multiple layers of epithelial cells. The deepest layer of the epidermis is where new skin cells are produced through cell division. This process is crucial for maintaining the skin's barrier function.

**Why the Correct Answer is Right**
The correct answer is related to the **stratum basale**, also known as stratum germinativum. This layer is in contact with the dermis and contains stem cells that proliferate to form new skin cells. The stratum basale is the deepest layer of the epidermis, where cell division occurs, and new cells are pushed upwards towards the skin's surface.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not correspond to the deepest layer of the epidermis.
**Option B:** This option is also incorrect as it refers to a different layer of the epidermis.
**Option C:** This option is incorrect because the correct answer is the layer where cell division primarily occurs.

**Clinical Pearl / High-Yield Fact**
The **stratum basale** is crucial for skin regeneration and is the target of many pathological processes, including skin cancers. Understanding the structure and function of the epidermis is essential for diagnosing and managing various skin conditions.

**Correct Answer:** D. Stratum basale