Regur soil is formed from the disintegration of _____.
A) Volcanic rocks
B) Hard rocks
C) Crystalline rocks
D) Soft rocks

Hint: This type of soil is commonly known as Black soil. It may also be addressed as ‘black cotton soil’ as cotton is the most widely grown crop in areas where this kind of soil is found.

Complete answer:
The ‘Regur Soil’ is the local name of the ‘Black Soil’, which is formed as a result of the disintegration of volcanic rock. The high content of organic matter and humus, also adds to its characteristic black colour and its highly fertile nature.

Let us analyze the given options:
Option A) Volcanic rocks – These rocks are formed from the cooling of lava which is expelled from a volcano. It is similar to igneous rocks but is different because it has a volcanic origin, unlike the igneous rocks. The disintegration of these volcanic rocks leads to the formation of Black soil, which is locally known as ‘Regur soil’. Therefore, this is the correct option.
Option B) Hard rocks – Hard rocks is a term used to describe any kind of rock that is not soft. It may be igneous or metamorphic rocks. All these rocks disintegrate and form different types of soils and not specifically the ‘regur soil’. Therefore, this option is incorrect.
Option C) Crystalline rocks – These rocks again can include both igneous and metamorphic rocks. These are basically those rocks which have been formed by the crystallization of a molten state. This again is a wide branch of rock which gives rise to several kinds of soils. Thus, this option is wrong.
Option D) Soft rocks – Soft rocks are a type of rocks which have very low strength and density in comparison to the hard rocks. This rock is also not so soft that it might turn into grains or soil. Though it may be seen scattered in soil or even with hard rocks, it is not considered as a parent for any kind of soil. Hence, this option is also wrong.

Thus, the correct answer is Option (A) Regur soil is formed from the disintegration of Volcanic rocks.

Note: Regur soil or black is predominantly found on the Deccan Lava plateau and the Malwa plateau, which includes states like Gujarat, Maharashtra, Karnataka and Madhya Pradesh. This region has moderate rainfall and an underlying layer of basaltic rock. This soil has an iron-rich granular structure that makes it resistant to erosion by wind and water.