The correct answer is West Bengal.

• Jaldapara National Park is a national park situated at the foothills of Eastern Himalayas in Alipurduar Sub-Division of Jalpaiguri district in West Bengal and on the bank of river Torsa.
• The river Torsha flows through this rain forest sanctuary and has an area of 141 sq.Km and altitude of 61 m.
• Jaldapara, the vast grassland with patches of riverine forests was declared a sanctuary in 1941 for protection of the great variety of flora and fauna, particularly the one-horned rhinoceros, an animal threatened with extinction.
• The Jaldapara Sanctuary covers 216 sq Km, is a mosaic of woods, grasslands, perennial streams, sandy river banks, and extensive belts of tall grass. 
• It contains a great diversity of flora and fauna of the mixed deciduous forest, grasslands, and river banks.
• The Malangi River also flows nearby from east to west.
• Drained by rivers Torsa, Malangi, Hollong, Chirakhawa, Kalijhora, Sissamara, Bhaluka, and Buri Torsa, the Sanctuary provides extensive grassland which is the last refuge to a wide variety of mammals, amphibians, reptiles, and birds.