The extraction of oil and natural gas in Assam is primarily done by:

Coal India Limited
Assam Mineral Development Corporation
Oil India Limited
ONGC

The correct answer is (c) Oil India Limited.

Oil India Limited (OIL) is an Indian state-owned oil and gas company headquartered in Duliajan, Assam. It is one of the largest producers of crude oil and natural gas in India. OIL was founded in 1959 as a joint venture between the Government of India and the Government of Assam. The company’s main activities include exploration, production, refining, and marketing of oil and gas. OIL has a presence in all the major oil and gas producing states in India, including Assam, Gujarat, Rajasthan, and Andhra Pradesh. The company also has a presence in the overseas markets, including Myanmar, Bangladesh, and Vietnam.

Coal India Limited (CIL) is an Indian state-owned coal mining company headquartered in Kolkata, West Bengal. It is the world’s largest coal producer by volume. CIL was founded in 1975 as a merger of nationalized coal mines in India. The company’s main activities include exploration, mining, and marketing of coal. CIL has a presence in all the major coal producing states in India, including Jharkhand, West Bengal, Odisha, and Chhattisgarh. The company also has a presence in the overseas markets, including Indonesia, Australia, and South Africa.

Assam Mineral Development Corporation (AMDC) is a state-owned mineral exploration and mining company headquartered in Guwahati, Assam. The company was founded in 1973 to promote the development of the mineral resources of Assam. AMDC’s main activities include exploration, mining, and marketing of minerals, including coal, iron ore, limestone, and bauxite. The company has a presence in all the major mineral producing districts in Assam, including Tinsukia, Dibrugarh, Sonitpur, and Goalpara.

ONGC Videsh Limited (OVL) is a wholly-owned subsidiary of Oil and Natural Gas Corporation (ONGC). OVL is an Indian state-owned oil and gas exploration and production company headquartered in New Delhi. The company was founded in 1980 to undertake overseas oil and gas exploration and production activities. OVL’s main activities include exploration, production, refining, and marketing of oil and gas. The company has a presence in over 20 countries, including Russia, Brazil, Venezuela, and Nigeria.