The correct answer is: b) Iron ore
Tamil Nadu has significant deposits of iron ore. The state is the second largest producer of iron ore in India, after Odisha. The main iron ore deposits in Tamil Nadu are located in the districts of Salem, Madurai, and Coimbatore.
Lignite (brown coal) is a type of coal that is less mature than bituminous coal or anthracite coal. It is found in large deposits in Tamil Nadu, but it is not of high quality and is not used for commercial purposes.
Bauxite is a type of ore that is used to produce aluminum. There are small deposits of bauxite in Tamil Nadu, but they are not commercially viable.
Copper is a metal that is used in a variety of products, including electrical wiring, plumbing, and construction. There are no significant deposits of copper in Tamil Nadu.