The correct option is (b).
Explanation
The UNESCO World Heritage List designates places of outstanding universal value. The "Mountain Railways of India" is a serial World Heritage Site that recognizes the bold and ingenious engineering solutions used to establish effective rail links through rugged, mountainous terrain during the 19th and early 20th centuries.
Option Analysis:
- Option (a) is Incorrect: The Dilwara Temples are a group of Svetambara Jain temples located in Mount Abu, Rajasthan, known for their extraordinary marble craftsmanship. However, they are not inscribed on the UNESCO World Heritage List.
- Option (b) is Correct: The Kalka-Shimla Railway was included in the UNESCO World Heritage List in 2008. It was added as an extension to the existing "Mountain Railways of India" designation, joining the Darjeeling Himalayan Railway (inscribed in 1999) and the Nilgiri Mountain Railway (inscribed in 2005).
- Option (c) is Incorrect: The Bhitarkanika Mangrove Area in Odisha is a significant ecosystem designated as a Ramsar Site and a National Park. It has been listed on the tentative list for UNESCO World Heritage status but has not been formally inscribed.
- Option (d) is Incorrect: The railway line from Visakhapatnam to Araku Valley is a scenic broad-gauge route in Andhra Pradesh, but it is not recognized as a UNESCO World Heritage Site.
Key Takeaway: The "Mountain Railways of India" UNESCO World Heritage Site consists of three specific narrow-gauge lines: the Darjeeling Himalayan Railway, the Nilgiri Mountain Railway, and the Kalka-Shimla Railway.