The correct answer is (a) Oil and natural gas.
Assam is one of the major oil and natural gas producing states in India. The state has a long history of oil and natural gas exploration and production. The first oil well in Assam was drilled in 1889, and the state has been a major producer of oil and natural gas ever since.
The oil and natural gas industry is the backbone of Assam’s industrial sector. The industry provides employment to a large number of people and contributes significantly to the state’s economy.
The other options are incorrect because they are not major industries in Assam.
(b) Textiles is not a major industry in Assam. The state has a small textile industry, but it is not as significant as the oil and natural gas industry.
(c) Cement is not a major industry in Assam. The state has a small cement industry, but it is not as significant as the oil and natural gas industry.
(d) Pharmaceuticals is not a major industry in Assam. The state has a small pharmaceutical industry, but it is not as significant as the oil and natural gas industry.