Correct Answer: (a) Cairn Energy
Solution:Cairn Energy PLC is one of Europe's leading independent oil and gas exploration and development companies and is listed on the London Stock Exchange. It is associated with the exploration and commercial production of oil in Barmer-Sanchore basin of Rajasthan. The 25-year contract for exploration and production of oil and gas from Cairn India's Barmer oil block in Rajasthan, in which ONGC holds a 30% stake, was due for renewal in 2020.