Answer: Ganga
Notes: Over the past 200 years, the Kosi River has shifted its course westward by over 100 km. Kosi is a transboundary river flowing through China, Nepal, and India, and is a major tributary of the Ganges. It is called the “Sorrow of Bihar” due to frequent and severe flooding in Bihar. Formed by the confluence of Sun Kosi, Arun Kosi, and Tamur Kosi, originating in the Himalayan region of Nepal and Tibet. About 48 km north of the India-Nepal border, it gathers tributaries and flows south through the Siwalik Hills at Chatra Gorge.
