The correct option is Assam.
Explanation
Dibru-Saikhowa is a significant protected area designated as both a National Park and a Biosphere Reserve, characterized by its unique riverine and swamp ecosystem.
Detailed Analysis:
- Location: The Dibru-Saikhowa Biosphere Reserve is situated in the state of Assam. It spans across the Dibrugarh and Tinsukia districts.
- Geographical Boundaries: The reserve is bounded by the Brahmaputra and Lohit rivers in the north and the Dibru river in the south. It is considered one of the largest swamp forests in north-eastern India.
- Ecological Significance: It is an identified Important Bird Area (IBA) and is notably famous for its population of feral horses. It also serves as a habitat for rare species such as the White-winged wood duck, water buffalo, and the Black-breasted parrotbill.
Key Takeaway: Dibru-Saikhowa is a Biosphere Reserve located in the floodplains of the Brahmaputra river in Assam.