Correct Option
The correct option isBrahmaputra Plain
Explanation
The Ganga-Brahmaputra basin encompasses diverse ecosystems ranging from mountain slopes to deltaic mangroves. The distribution of wildlife within this basin is determined by specific habitat requirements such as vegetation type, terrain, and water availability. The Indian One-Horned Rhinoceros (Rhinoceros unicornis) specifically requires alluvial grasslands and swampy marshes to thrive.
Option Analysis
- Brahmaputra Plain Brahmaputra Plain: Correct. The Brahmaputra Plain, particularly within the state of Assam, is the primary stronghold of the one-horned rhinoceros. The region's topography consists of vast alluvial floodplains, tall grasslands, and wetlands, which constitute the ideal habitat for this species. Major protected areas such as Kaziranga National Park, Manas National Park, and Pobitora Wildlife Sanctuary are located in this plain.
- Ganga Plain Ganga Plain: Incorrect. While the historical range of the rhinoceros extended across the entire Indo-Gangetic plain, the current population in the Ganga basin is fragmented and largely restricted to the Terai arc (foothills) rather than the main agricultural plains of the Ganga.
- Delta Area Delta Area: Incorrect. The Delta area (Sundarbans) is dominated by mangrove forests and saline waters. This ecosystem is the prime habitat for the Royal Bengal Tiger and Estuarine Crocodile, but it does not support rhinoceros populations.
- Mountain Slopes Mountain Slopes: Incorrect. The one-horned rhinoceros is a megaherbivore adapted to flat, marshy lowlands and grasslands. It is not adapted to the steep, rugged terrain of mountain slopes, which are inhabited by species like the Snow Leopard or Musk Deer.
Key Takeaway: The Brahmaputra Plain is the most significant habitat for the one-horned rhinoceros due to the presence of extensive alluvial grasslands and swamps, most notably in Kaziranga National Park.