The correct answer is: a) Thermal power plants.
Coal is a fossil fuel that is used to generate electricity in thermal power plants. It is also used in the production of steel and other metals, as well as in the manufacture of chemicals.
Bihar is one of the largest producers of coal in India. The state has an estimated reserve of 29 billion tonnes of coal, which is about 10% of the country’s total reserve. The coal in Bihar is mostly of the bituminous variety, which is a good quality coal that is suitable for use in thermal power plants.
Thermal power plants are a major source of electricity in India. In 2017, thermal power plants generated about 60% of the country’s electricity. The use of coal in thermal power plants has been criticized for its environmental impact, as coal combustion releases greenhouse gases into the atmosphere. However, coal is still a major source of energy in India, and it is likely to remain so for the foreseeable future.
The other options are incorrect because they do not use coal as a major input. Aluminum smelting uses bauxite ore, brick manufacturing uses clay, and gold mining uses gold ore.