Final answer:
The nail bed, if destroyed, cannot grow back, while other parts of the nail such as the cuticle, nail plate, and nail root can regenerate to an extent. The nail plate is made of dead keratinocytes, and cutting the cuticle, another feature, is not advisable.
Step-by-step explanation:
You asked which part of the nail will not grow back once destroyed. Of the options given, the nail bed is the one that, if destroyed, cannot regenerate, while the cuticle, nail plate, and nail root can regenerate to some extent if damaged.
The nail bed is a specialized structure that supports the nail body, while the nail plate is the hard part of the nail that we can see. The nail grows from the nail matrix located at the nail root. The matrix is where new nail cells are produced and pushed forward as they harden.
It is not recommended to cut the cuticle during a manicure since it serves as a protective barrier against infections. The cuticle is also sometimes referred to as the eponychium. As for the nail plate, it is composed of densely packed dead keratinocytes.