Why is studying a Himalayan river from source to mouth necessary in difficult questions?

Correct answer: It explains origin, tributaries, landforms and final outlet

Studying a Himalayan river from its source to its mouth gives a complete picture of its drainage system. The source shows where the river begins and the physical conditions that start its flow. As the river travels, tributaries join it, increasing its water and sediment. Its course also reveals valleys, gorges, floodplains, meanders, and other landforms. The mouth shows where the river finally enters another river, a lake, or the sea, and whether it forms a delta or estuary.

Option A is correct because a river is not understood by looking at only one point. A source-to-mouth study connects origin, tributaries, relief, landforms, confluences, and final outlet. These details help explain both the river’s physical behaviour and its geographical importance. The other options mention colour, taste, or forest height, which are not the purpose of studying a river’s complete course. The whole route gives the clearest understanding.