Correct Answer: at a very low gradient

Solution : The correct answer is at a very low gradient.

Oxbow lakes are formed when the river bends and separates from the main river, and flows in a curved shape, which later forms a separate water body. A horseshoe lake, a cutoff lake, or a loop lake are other names for it. It is formed when a river is flowing at a very low gradient. It is usually formed in the mature stage of the evolution of the river. Kanwar Lake is the largest oxbow lake in India and Asia. It is located in Begusarai district of Bihar.