The correct answer is: B. Khadar
The alluvial plains extended between Yamuna and Ghaggar rivers is known as Khadar. Khadar is a type of floodplain that is formed by the deposition of silt and sand by rivers. It is a relatively flat area with a low elevation. The soil in Khadar is fertile and is suitable for agriculture.
Bangar is a type of upland plain that is formed by the deposition of sand and gravel by rivers. It is a relatively high area with a steep slope. The soil in Bangar is not as fertile as the soil in Khadar.
Undulating plain is a type of plain that has a gently rolling surface. It is formed by the deposition of sediments by rivers and glaciers. The soil in undulating plain is fertile and is suitable for agriculture.
Marshy land is a type of land that is covered by water or has a high water table. It is formed by the deposition of sediments by rivers and glaciers. The soil in marshy land is not as fertile as the soil in other types of plains.