Which term best describes a situation where immediate medical assistance is needed?

The term that best describes a situation where immediate medical assistance is needed is "Emergency Situation." This term encompasses any occurrence that poses an immediate risk to health, life, property, or the environment, requiring urgent intervention. In the context of security and public safety, an emergency situation often triggers a rapid response from medical personnel, law enforcement, or emergency services to mitigate potential harm.

The other choices — while relevant in their specific contexts — do not fully capture the urgency and critical nature of requiring immediate medical assistance as effectively as "Emergency Situation." A "Medical Situation" may refer to various health-related issues but does not inherently imply that immediate action is required. "Health Crisis" suggests a significant health issue but might not necessarily require immediate assistance. "First Aid Incident" specifically refers to situations where first aid is provided, but this term implies that there is an injury or issue already recognized rather than the broader category of urgent emergencies.