The correct answer is option 3, Kolkata. The headquarters of Metro Railway Zone is located in Kolkata, West Bengal.
Option 1, New Delhi, is incorrect. Although New Delhi is the capital city of India and has a significant railway infrastructure, the headquarters of the Metro Railway Zone is not located there.
Option 2, Mumbai, is also incorrect. Mumbai, the financial capital of India, has a well-developed local train network, but it is not the location of the headquarters of the Metro Railway Zone.
Option 4, Chennai, is also incorrect. Chennai, the capital city of Tamil Nadu, has a metro system, but it is not the headquarters of the Metro Railway Zone.
Therefore, the correct answer is option 3, Kolkata. It is important to mention that the headquarters of other railway zones in India may be located in different cities, but for the Metro Railway Zone, the headquarters is specifically in Kolkata.