How does the concept of water divide help in understanding Himalayan river basins?

Correct answer: Highland separates different drainage areas

The direct answer is A: highland separates different drainage areas. A water divide is a ridge, hill or higher land that directs rainwater toward different sides. Water falling on one side enters one river basin, while water falling on the other side enters another basin. In Himalayan terrain, high mountain ridges can therefore mark the boundaries between drainage basins, even though the exact landscape may be complex. Option A is correct because it explains both the physical feature and its role in defining a basin. Option B is wrong because a river mouth is the place where a river enters a sea, lake or another river; it is not a divide. Option C is wrong because a distributary is a branch leaving the main channel, not a boundary ridge. Option D is wrong because sea waves are produced by marine forces and are unrelated to the definition of a water divide. Memory cue: divide means divide drainage, not divide the river mouth.