Answer: 4
Notes: Assam state of India is rich in mineral resources. Petroleum or crude oil is the most important of them all. In fact, Assam is the mother of Indian petroleum industry. In India, petroleum was first discovered in Assam. It was Digboi in Assam where the first Oil Refinery in Asia came up. Indian petroleum companies like OIL and ONGC were born out of Assam. Four Oil Refineries of Assam are Digboi Refinery, Noonmati refinery in Guwahati, Dhaligoan refinery near Bongaigaon, Numaligarh Refinery of Golaghat district.
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