Correct Option
The Gondwana rock system is considered the most important rock system in India primarily due to its vast coal reserves. These formations account for over 90% of India's total coal reserves. Dating back primarily to the Carboniferous and Permian periods, these sedimentary basins are the principal source of bituminous and sub-bituminous coal, essential for thermal power generation. Significant coalfields are found in regions such as the Damodar Valley (Jharkhand, West Bengal), Son-Mahanadi Valley, and Godavari Valley.
Incorrect Options
Option (a): Limestone reserves are predominantly associated with the Vindhyan rock system, not the Gondwana system.
Option (c): Black cotton soils, also known as Regur, are primarily formed from the weathering of basaltic rocks of the Deccan Traps, not the Gondwana formations.
Option (d): As option (b) provides a valid and appropriate reason for the importance of Gondwana rocks, this option is incorrect.