Final answer:
A firefighter should sign in with the Rapid intervention crew or team (RIC/RIr) before entry into an immediately dangerous to life and health (IDLH) area. So, the correct answer is option d.
Step-by-step explanation:
In an immediately dangerous to life and health (IDLH) area, a firefighter should sign in with the Rapid intervention crew or team (RIC/RIr) before entry.
The Rapid Intervention Crew or Team (RIC/RIr) is a specially trained group of firefighters whose primary role is to rapidly respond and rescue firefighters in distress during firefighting operations. They are responsible for ensuring the safety of firefighters operating in hazardous environments.
By signing in with the RIC/RIr, a firefighter ensures that there is an immediate backup team ready to provide assistance in case of emergency.
So, the correct answer is option d.