Final answer:
The potential risk of leaving the protruding rebar unattended is a tripping hazard.
Step-by-step explanation:
The potential risk of leaving the protruding rebar unattended is a tripping hazard. If someone were to accidentally trip over the protruding rebar, they could suffer serious injuries such as cuts, bruises, or even broken bones. It is important to always keep the work area clear and secure any hazardous objects to prevent accidents.