The correct answer is: Alluvial soil.
Alluvial soil is a type of soil that is formed by the deposition of sediment from rivers and streams. It is typically found in floodplains and deltas. Alluvial soil is very fertile and is often used for agriculture.
Black soil is a type of soil that is rich in organic matter. It is typically found in the tropics and subtropics. Black soil is very fertile and is often used for agriculture.
Red soil is a type of soil that is rich in iron oxide. It is typically found in tropical and subtropical regions. Red soil is not as fertile as black soil, but it is still suitable for agriculture.
Laterite soil is a type of soil that is formed by the weathering of rocks in tropical and subtropical regions. It is typically rich in iron and aluminum oxides. Laterite soil is not very fertile and is not suitable for agriculture.
The Imphal Valley is a valley in the state of Manipur in India. It is a fertile valley that is home to a number of rivers and streams. The soil in the Imphal Valley is predominantly alluvial soil.