Final answer:
The epidermal layer capable of undergoing mitosis is the stratum basale, which is the innermost layer containing stem cells that divide to form new keratinocytes.
Step-by-step explanation:
Of the five epidermal cell layers, the only one that can undergo mitosis is the stratum basale. The stratum basale is the innermost or the deepest layer of the epidermis. It contains stem cells, known as basal cells, which divide to form all the keratinocytes of the epidermis. These keratinocytes are initially cube-shaped and almost keratin-free. As they divide and produce new cells, the older ones are pushed upward, eventually becoming part of the upper layers of the epidermis.
The other layers, including stratum spinosum, stratum granulosum, stratum lucidum (when present), and stratum corneum, do not undergo mitosis. The stratum lucidum is only found in thick skin on the palms and soles, consisting of dead keratinocytes, while the outermost stratum corneum is a layer of flat, dead cells that form a protective barrier.
Therefore, the correct answer is a. stratum basale.