When almost all the elevated portions are worn down by river erosion reducing an area to almost a plain region, it is termed as

Answer: Option D

When almost all the elevated portions are worn down by river erosion reducing an area to almost a plain region, it is termed as Peneplain. Peneplain is a region that is almost a plain. It is formed due to erosion by rivers and rain, that continues until almost all the elevated portions are worn down; the most resistant rocks generally stand above the general level of the land.