Final answer:
The appropriate emergency plan action that takes place after an emergency has occurred is Response.
Step-by-step explanation:
After an emergency has occurred, the appropriate emergency plan action is Response. Response refers to the immediate actions taken to address the situation and protect lives and property. This includes activities such as evacuations, search and rescue efforts, providing medical assistance, and restoring essential services.
Protection relates to actions taken to guard against emergencies, while Relief refers to assistance and support provided to individuals and communities during and immediately after an emergency. Lastly, Mitigation involves efforts to reduce the effects of future emergencies.
In the context given, Plan A appears to be the default action taken when a threat is not believed to be real, whereas Plan B represents more cautious steps to mitigate the potential threat.