Which one of the following is the appropriate reason for considering the Gondwana rocks as most important of rock systems of India?

1. (a)More than 90% of limestone reserves of India are found in them
2. (b)More than 90% of India's coal reserves are found in them
3. (c)More than 90% of fertile black cotton soils are spread over them
4. (d)None of the reasons given above is appropriate in this context