Which sign is used only where an immediate life-threatening hazard exists?

The correct choice emphasizes the importance of communication regarding immediate life-threatening hazards. A danger sign is specifically intended to convey the presence of a severe hazard that poses an immediate risk of harm or death if not addressed. These signs typically feature a prominent red background along with specific graphics or text indicating the nature of the danger.

Such signs alert individuals to immediate threats, prompting them to take urgent action to protect themselves and others. In contexts where a quick response is vital, the clear and direct messaging of danger signs helps to ensure that individuals can quickly recognize the severity of the situation and respond accordingly to mitigate risks.

Other sign types, such as warning signs and caution signs, are used to indicate potential hazards but do not necessarily denote an immediate life-threatening condition. Mandatory signs typically indicate required actions or behaviors that must be followed, but they do not convey the urgency associated with danger signs.