The correct answer is Option 3: Nilgiri Hills.

The Nilgiri Hills are a range of mountains located in the westernmost part of Tamil Nadu, in southern India. They are situated at the meeting point of the Eastern Ghats and the Western Ghats, making them an important geographical feature in the region. The word "Nilgiri" translates to "Blue Mountains" in the local language, and they are often referred to as the "Queen of the Hills."

Here`s a more detailed reasoning for why the Nilgiri Hills are the correct answer:

1. Geographical Location: The Nilgiri Hills are located in the southern Indian states of Tamil Nadu and Kerala. They are part of the larger Western Ghats mountain range, which runs parallel to the western coast of India. The Eastern Ghats, on the other hand, are situated to the east of the Deccan Plateau and are not directly connected to the Nilgiri Hills. Therefore, the Nilgiri Hills are found at the point where the Eastern Ghats and Western Ghats meet.

2. Ecological Significance: The Nilgiri Hills are renowned for their rich biodiversity and serve as an important ecological hotspot. They are home to several national parks and wildlife sanctuaries, including the Mudumalai National Park, Bandipur National Park, and Silent Valley National Park. These areas provide habitat to a wide range of flora and fauna, including several endangered species.

3. Hill Stations: The Nilgiri Hills are also famous for their hill stations, which attract tourists from all over the world. The most well-known hill stations in the Nilgiri Hills include Ooty (Udhagamandalam), Coonoor, and Kotagiri. These hill stations are known for their pleasant climate, tea and coffee plantations, picturesque landscapes, and colonial-era architecture.

4. Nilgiri Mountain Railway: The Nilgiri Hills are connected to the plains by the Nilgiri Mountain Railway, a UNESCO World Heritage site. This narrow-gauge railway was built in the 19th century and still operates today. It is a popular tourist attraction, offering scenic views of the surrounding hills and valleys.

In summary, the Nilgiri Hills are the mountains where the Eastern Ghats and Western Ghats converge. They are known for their ecological significance, hill stations, and the Nilgiri Mountain Railway, making them a prominent landmark in the southern part of India.