Question

Why plains are thickly populated?

Answer 1

Plains are thickly populated because the soils are very fertile and fertile soils provide a good place for cultivating crops. Also, the plains are surrounded by rivers and rivers are quite, quite useful. The transportation is also easy in plains.

Answer 2

Answer:

More flat land is available for building houses. Soil is fertile and more land for cultivation is  available. Construction of transport network is easy.