Disaster management in India is organized through a multi-tier institutional structure established by the Disaster Management Act of 2005 to ensure a proactive and coordinated response to natural and man-made calamities.
Step 1: Analyze the options.
(A) National Disaster Management Authority (NDMA): This is the highest policy-making body for disaster management in India. It is headed by the Prime Minister and is responsible for laying down policies, plans, and guidelines for disaster management.
(B) National Disaster Response Force (NDRF): While a crucial organization, the NDRF is a specialized force meant for disaster response and rescue operations. It works under the guidance of the NDMA but is not the "apex body" for policy and governance.
(C) Rural Disaster Management Committee: These committees function at the local or village level to manage disasters within rural communities but do not have national jurisdiction.
(D) Office of District Magistrate: The DM (or District Collector) heads the District Disaster Management Authority (DDMA). While they are the apex authority at the district level, they are not the apex body for the entire country.
Step 2: Conclusion.
The National Disaster Management Authority (NDMA) serves as the top-most (apex) body governing disaster management across India.
Final Answer:
\[
\boxed{(A) \, \text{National Disaster Management Authority}}
\]