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

Answer: (b) fissure volcanic rock

Black soil (regur) formed from the basalt of the Deccan Traps — lava that poured out of long fissures about 66 million years ago.

The idea

Black soil is rich in lime, iron, magnesium and potash but poor in nitrogen and phosphorus. It holds moisture, swells when wet and cracks when dry — “self-ploughing” — ideal for cotton.

Fissure eruptions → Deccan basalt → weathering → black cotton soil (regur)

Why the others are wrong

(a) Brown forest soil is a soil itself, not a parent rock.

(c) Granite and gneiss give red soils.

(d) Shale and limestone give other sedimentary soils.

The trap

Granite (c) is the parent rock of the Peninsula’s RED soils — the neighbours of black soil. Colour tells you the parent rock.