Hint: The region is located south of the outer foothills of the Himalayan Mountain Range, the Shivalik Hills and north of the Indo-Gangetic Plain. This region also lies between the rivers Yamuna and Brahmaputra. The region is well known for its various kinds of plants and is the home for wildlife and a wide range of birds.
Complete answer: Option A: Kankar region covers the western part of the country through a narrow corridor in Rajasthan, and extends into the plains of Gujarat. In the peninsular area, this region is found in the deltas of the east coast and in the river valleys. Thus, option A cannot be the right option.
Option B: Though Bhabar region covers a region south of the Lower Himalayas and the Shivalik Hills, it does not represent a region that is wet, swampy and marshy, rather the soil of this region is the alluvial apron of sediments washed down from the Himalayan mountains for a long period of time. Thus, option B cannot be the answer.
Option C: Khadar is a region that is also present in the northern plains but this region shows features of having fresh alluvial deposits from the mountains and not of wet, swampy and marshy soil.Hence, option C cannot be the answer as well.
Option D: Terai is a region of northern India and southern Nepal running parallel to the lower ranges of the Himalayas. It is a narrow strip of undulating marshland which has formed formerly and it stretches from the Yamuna river in the west to the Brahmaputra river in the east. At the northern part of the region there are several springs forming many streams and rivers which make the land moist and damp. Therefore, the region demonstrates features of wet, swampy land with marshes all along.
Hence, the correct answer to the question is Option D, Terai.
Note: Terai region experiences a tropical savanna type of climate with dry and cool winters and warm and moist summer. The lower belt of the Terai region is characterised by tall grasslands, scrub savannah, sal forests and clay rich swamps. In West Bengal, this Terai region is named as ‘Dooars’.