The narrow, pebble-studded belt at the foot of the Shiwaliks, where the streams descending from the mountains disappear underground, is called the

The correct answer is B, Bhabar. Where the rivers leave the hills they drop their coarsest load, and the resulting belt of gravel and pebbles is so porous that the smaller streams sink into it and vanish. This belt, about eight to sixteen kilometres wide, runs along the whole northern edge of the plains and is known as the bhabar.

Option A, the terai, is the belt immediately south of the bhabar, where the same streams come to the surface again, creating a marshy and once heavily forested tract. Option C, bhangar, refers not to a position at the foot of the hills but to the older alluvium of the plains, lying above the flood level and often containing lime nodules called kankar. Option D, khadar, is the newer alluvium of the active floodplains, renewed by fresh silt at every flood. Bhabar and terai are a pair and are the two most often interchanged in answer sheets.