Which tool is used to clean under the free edge of the nail?

The tool used to clean under the free edge of the nail is the nail brush or orangewood stick.

A nail brush is specifically designed to clean the surface of the nails and any debris that accumulates underneath the free edge, which is the area at the tip of the nail that extends beyond the fingertip. The bristles of the nail brush effectively sweep away dirt and residue without damaging the nail or surrounding skin.

On the other hand, an orangewood stick, often used in manicure procedures, can also be employed to gently push back the cuticle or to remove debris from underneath the free edge. It is made of wood and can be easily maneuvered to clean the nail without causing injury.

The other tools mentioned have specific functions that do not primarily involve cleaning beneath the free edge: nail clippers are used to trim nails, cuticle removers are designed to assist with the removal of excess cuticle, and buffing blocks are utilized to smooth the surface of the nail for a polished finish. Thus, the combination of both the nail brush and orangewood stick makes option C the most suitable answer for cleaning under the free edge of the nail.