Answer:
D) Triggered following a declaration by the Secretary of Homeland Security.
Step-by-step explanation:
The National Response Framework (NFR) is a guide to know how the nation would respond if an emergency or disaster happens (Option B discarded). The NFR could be triggered by a natural disaster or a terrorist attack (Option C discarded).
The NFR starts to run after a declaration by the Secretary of Homeland Security. After that, the military field is incorporated under the command of the President of the United States.
I hope this answer helps you.