The correct answer is option 3, "Bhabar". When streams and rivers from the mountains flow into the plains, they carry a lot of heavy materials like rocks and boulders with them. These materials get deposited in various landforms found in the plains.

Option 1, "Khadar", is incorrect because khadar refers to the fertile soil deposited by floods in the floodplains of rivers.

Option 2, "Bhangar", is incorrect because bhangar refers to the older alluvial deposits found at a higher elevation in the floodplain.

Option 4, "Terai", is incorrect because terai refers to the low-lying area at the foothills of the Himalayas, characterized by marshy and swampy conditions.

Therefore, the correct option is 3, "Bhabar", as it is the landform where heavy materials brought by streams and rivers are deposited in the plains.