The correct answer is: a) Coal
Coal is the most significant industrial sector in Assam. The state has large reserves of coal, which are used to generate electricity and produce steel. The coal industry is a major employer in Assam, and it contributes significantly to the state’s economy.
Iron ore is also a significant mineral resource in Assam, but it is not as important as coal. Iron ore is used to produce steel, and the state has a number of steel mills. However, the iron ore industry is not as large as the coal industry, and it does not employ as many people.
Petroleum is not a significant mineral resource in Assam. There are some small oil fields in the state, but they do not produce enough oil to be commercially viable. The petroleum industry does not play a major role in the Assamese economy.
Bauxite is also not a significant mineral resource in Assam. There are some bauxite deposits in the state, but they are not large enough to be commercially viable. The bauxite industry does not play a major role in the Assamese economy.
In conclusion, the most significant industrial sector in Assam is based on the extraction and processing of coal. Coal is a major employer in Assam, and it contributes significantly to the state’s economy.