Water retention and cracking in black soil are both related to which property?

Correct answer: Shrink and swell nature

The direct answer is A, shrink-and-swell nature. Black soil contains a large amount of clay, especially clay that expands when wet and contracts when dry. Step by step: water enters the clay particles; the soil swells and holds moisture; drying removes water; the particles contract and wide cracks may form. Therefore water retention and cracking are two results of the same property. B, coral hardness, concerns marine organisms and does not explain soil behaviour. C, glacial accumulation, concerns deposits made by glaciers. D, tidal drainage, concerns coastal water movement. A is correct. This soil is common in the Deccan region and is valuable for cotton, but those facts are examples or associations, not the property itself. Exam cue: black soil = clay + moisture retention + shrinkage cracks.