The correct answer is A. Orissa coast.
Thorium is a naturally occurring radioactive metal that is found in monazite sand. Monazite sand is a heavy, black sand that is found in beach sand and river sand. It is the most important source of thorium in India.
The Orissa coast is the most extensive area of monazite sand deposits in India. The monazite sand deposits on the Orissa coast are estimated to contain about 100,000 tonnes of thorium.
The monazite sand deposits on the Orissa coast are mined by open-pit mining. The monazite sand is then processed to extract the thorium. The thorium is then used to produce nuclear fuel.
The monazite sand deposits on the Orissa coast are a valuable resource for India. The thorium from these deposits can be used to produce nuclear fuel, which can be used to generate electricity. Nuclear power is a clean and efficient source of energy, and it can help India to reduce its dependence on fossil fuels.
The monazite sand deposits on the Orissa coast are also a valuable resource for the local economy. The mining of monazite sand provides jobs for local people, and the processing of thorium provides jobs for scientists and engineers. The monazite sand deposits on the Orissa coast are a valuable resource for India, and they are a valuable resource for the local economy.
The other options are incorrect because they are not areas where monazite sand deposits are found.