Final answer:
The living skin bordering the root and sides of a fingernail or toenail is the perionychium (D). The nail matrix is where nail growth occurs, the eponychium or cuticle covers the nail bed, and the hyponychium is the part furthest from the nail growth center.
Step-by-step explanation:
The living skin bordering the root and sides of a fingernail or toenail is known as the perionychium. This is part of the answer to the multiple-choice question, where the correct option is D) Perionychium.
It's important to differentiate between this and the other options: A) Matrix refers to the deep layer of epidermal tissue where nail growth occurs, B) Eponychium is also known as the nail cuticle and is the fold of epithelium that extends over the nail bed, and C) Cuticle is a layer of dead epithelial cells that overlaps and covers the edge of the nail plate.
Regarding the question about which part is furthest from the nail growth center, the correct answer is B) hyponychium, which is the area beneath the free edge of the nail, farthest from the cuticle.