What is the main physical reason for distributaries in the Ganga-Brahmaputra delta?

Correct answer: Division of main channel due to reduced slope and sediment deposition near the mouth

Direct answer: Option A is correct. Near the mouth of a river, the land becomes flatter, so the river loses speed and its ability to carry sediment. The Ganga and Brahmaputra bring a very large sediment load. When this sediment is deposited near the delta, the main channel becomes partly blocked or divided, and the water finds several lower paths to the sea. These smaller branches flowing away from the main river are distributaries. Option A gives both essential physical causes: reduced slope and sediment deposition. Option B describes strong erosion in the upper mountains, not the immediate cause of delta distributaries. Option C concerns the Western Ghats, which are unrelated to this delta. Option D concerns low rainfall in the Thar and is irrelevant. A distributary branches away from the main river near its mouth; a tributary joins a main river upstream. This distinction is a common exam cue.