The correct answer is: D. Trivandrum
Trivandrum is the southernmost railway station in India. It is located in the state of Kerala. The station is a major hub for both passenger and freight traffic. It is also a major tourist destination.
Chennai is the capital of the state of Tamil Nadu. It is the fourth most populous city in India. The city is a major center for commerce, industry, and education. Chennai has a number of railway stations, but the southernmost one is Chennai Egmore.
Cochin is a city in the state of Kerala. It is a major port city and a popular tourist destination. The city has a number of railway stations, but the southernmost one is Ernakulam Junction.
Kanyakumari is a town in the state of Tamil Nadu. It is located at the southernmost tip of India. The town is a popular tourist destination. It has a railway station, but it is not the southernmost railway station in India.