The black cotton soil of India has been formed due to the weathering of

Black soils are mineral soils characterized by a black surface horizon, rich in organic carbon, extending to a depth of at least 25 cm.

These soils are primarily formed due to the weathering and erosion of basalt rocks (fissure volcanic rock).

Basalt is an aphanitic extrusive igneous rock that forms from the rapid cooling of low-viscosity lava, which is rich in magnesium and iron.

In India, black soil is predominantly found in states such as Maharashtra, Gujarat, Madhya Pradesh, and Karnataka.

Hence, option (b) is the correct answer.