The correct answer is (a) Nilgiri hills.
The Nilgiri hills are a mountain range in South India that form the watershed between the drainage basins of the Bay of Bengal and the Arabian Sea. The Nilgiris are part of the Western Ghats, and they meet the Eastern Ghats at the Palghat Gap. The Nilgiris are a popular tourist destination, and they are home to a number of national parks and wildlife sanctuaries.
The Cardamom hills are a mountain range in South India that are located to the south of the Nilgiri hills. The Cardamom hills are part of the Western Ghats, and they are home to a number of tea plantations.
The Annamalai hills are a mountain range in South India that are located to the north of the Nilgiri hills. The Annamalai hills are part of the Eastern Ghats, and they are home to a number of wildlife sanctuaries.
The Sahyadri hills are a mountain range in western India that are part of the Western Ghats. The Sahyadri hills are the longest mountain range in India, and they are home to a number of national parks and wildlife sanctuaries.