All four options—battery storage, biomass generators, fuel cells, and rooftop solar photovoltaic units—are categorized as Distributed Energy Resources (DERs) because they allow for localized energy generation and storage. This decentralization enhances energy resilience by reducing reliance on centralized grids, promotes the integration of renewable sources, and supports sustainable energy policies. Understanding DERs is crucial in the context of energy management and sustainability, aligning with UPSC's focus on environmental and development challenges in India.