Attached to the base of the nail under the skin, and inside the mantle is the?

The nail root is an essential part of nail anatomy and is located under the skin, specifically at the base of the nail. It is the portion of the nail that is not visible from the outside because it is hidden beneath the surrounding tissue and skin. The nail root is responsible for the growth of the nail, as it is connected to the nail matrix, which produces the cells that form the nail plate.

The nail bed, while crucial for supporting the nail, is the area of skin's surface beneath the nail plate and is not attached to the skin in the same manner as the root. The cuticle is a thin layer of skin that overlaps the nail plate, providing a barrier to protect the nail matrix from infection, but it is not attached to the nail itself in the way the root is. Finally, the nail matrix is also beneath the skin and plays a role in nail formation, but the correct answer focuses on the structure specifically attached at the base of the nail.

With this understanding, the nail root's attachment and its role in the overall nail structure clarify why it is the correct choice.