Final answer:
The correct answer is c. The correct term for the area that must be kept clear in case a piece of a structure collapses during an incident is the collapse zone. This zone is essential for ensuring the safety of emergency responders and the public by preventing injuries from falling debris.
Step-by-step explanation:
The area that must be kept clear in case a piece of a structure collapses during an incident is called the collapse zone. An evacuation zone, such as the one set up around a plant after an accident with radioactive fallout, is generally established to protect the public from dangers. A collapse zone is particularly designated around structures at risk of collapse to ensure safety for emergency responders and others nearby.
This zone typically extends out from the base of the structure a distance of one to one and a half times the height of the structure. It's a proactive safety measure to prevent injury from falling debris. In the context of emergency services, other relevant terms like cold zone, control zone, and crowd control zone refer to different safety protocols and areas with specific functions and restrictions.