Question

Why the Northern Indian Plain is thickly populated? Mention the two states of Northern Plains

with high population density.

Answer 1

The Northern Plains of India are thickly populated because it is agriculturally very productive. The high productivity is because of the deposit of fertile alluvial soil across the plains , adequate water supply for agriculture due to the presence of many rivers and favourable climate.
Two states in Northern Plains which have high population density are : West Bengal and Uttar Pradesh.