Which area contains cells that undergo mitosis and retain the ability to differentiate?

The undifferentiated zone is the correct answer because it refers to a specific area in tissues where cells have not yet specialized and retain the capacity for both mitosis, the process of cell division, and differentiation into specialized cell types. This zone is crucial for tissue growth and repair, as it contains stem cells that can proliferate and eventually give rise to various differentiated cell types.

In contrast, the matrix zone typically refers to the area where new cells are formed and pushed outward but may not specifically indicate the retention of differentiation ability over time. The differentiated zone is comprised of cells that have already specialized and are no longer capable of mitosis; therefore, while these cells perform specific functions, they do not have the versatility seen in the undifferentiated zone. The keratogenous zone relates primarily to keratin production and often refers to the outer layer of cells that are already differentiated and primarily dead or degenerating. Hence, it lacks the ability to undergo mitosis and differentiation, affirming that the undifferentiated zone is the area where cells actively divide and maintain differentiation potential.