Correct Option
The area marked 3 on the map corresponds to the Krishna-Godavari (KG) and Cauvery deltaic basins along India's eastern coast, primarily in Andhra Pradesh and Tamil Nadu. This region is part of India's Eastern Offshore Petroleum Basin. Commercial production of mineral oil and natural gas commenced in this area during the 1990s, with significant contributions from fields such as Narimanam and Kovilappal in the Cauvery Basin, and the Krishna-Godavari Basin offshore blocks. This aligns with the question's context of new commercial production starting around 1998.
Incorrect Options
Region 1: This area represents the Gujarat and Rajasthan sedimentary basins (e.g., Cambay Basin, Barmer Basin). While these are significant oil-producing regions in India, commercial production here was well-established much earlier than the 1990s, making it unsuitable for the criterion of "commercial production has started" in the context of the question.
Region 2: This region indicates the Assam-Arakan Basin. This is one of India's oldest oil-producing areas, with commercial extraction dating back to the late 19th century (e.g., Digboi oilfield). Therefore, it does not fit the description of an area where commercial production started in the period relevant to the question.
Region 4: This area broadly covers parts of the Western Ghats or Karnataka. This geological region is not known for significant commercial deposits or production of mineral oil.