The correct answer is: a) The Nilgiris, Dharmapuri, Salem.
The Nilgiris, Dharmapuri, and Salem districts are among the districts in Tamil Nadu with a significant tribal population. The Nilgiris district is home to the Todas, Kotas, and Irula tribes. The Dharmapuri district is home to the Kurumbar, Paniyar, and Irular tribes. The Salem district is home to the Soliga, Yerukula, and Irular tribes.
The other options are incorrect. Chennai, Coimbatore, and Madurai are not among the districts in Tamil Nadu with a significant tribal population. Coastal districts are not among the districts in Tamil Nadu with a significant tribal population. The Kaveri Delta region is not among the districts in Tamil Nadu with a significant tribal population.
The Nilgiris district is a district in the Indian state of Tamil Nadu. It is located in the Western Ghats and is known for its tea plantations, coffee plantations, and wildlife sanctuaries. The district is also home to the Nilgiris Hills, which are the highest mountain range in Tamil Nadu. The Nilgiris district is home to a number of tribal groups, including the Todas, Kotas, and Irula.
The Dharmapuri district is a district in the Indian state of Tamil Nadu. It is located in the northern part of the state and is known for its forests, hills, and rivers. The district is also home to a number of tribal groups, including the Kurumbar, Paniyar, and Irular.
The Salem district is a district in the Indian state of Tamil Nadu. It is located in the northern part of the state and is known for its industries, agriculture, and education. The district is also home to a number of tribal groups, including the Soliga, Yerukula, and Irular.