The correct answer is (a) Narmada.
The Narmada River is the fifth-longest river in India, flowing from Amarkantak in Madhya Pradesh to the Arabian Sea at Bharuch in Gujarat. It is the largest river basin in India that does not flow into the Ganges. The Narmada basin is home to over 30 million people and is a major source of irrigation, drinking water, and hydroelectric power.
The Cauvery River is the longest river in the Indian state of Tamil Nadu and the second-longest river in the Deccan Plateau. It flows through the states of Karnataka, Kerala, and Tamil Nadu, and its basin is home to over 80 million people. The Cauvery is a major source of irrigation, drinking water, and hydroelectric power.
The Tapi River is a river in central India that flows through the states of Madhya Pradesh, Maharashtra, and Gujarat. It is the sixth-longest river in India and the largest river in the Malwa Plateau. The Tapi basin is home to over 20 million people and is a major source of irrigation, drinking water, and hydroelectric power.
The Mahanadi River is a river in eastern India that flows through the states of Chhattisgarh, Odisha, and Jharkhand. It is the eighth-longest river in India and the largest river in the eastern Indian states. The Mahanadi basin is home to over 30 million people and is a major source of irrigation, drinking water, and hydroelectric power.