Explanation:

- Option 1: Kolkata - Kolkata is a major city in India, known for its cultural heritage and historical significance. However, by the Census 2011 data, it was not the most populated metro city.

- Option 2: Chennai - Chennai is a significant commercial and cultural hub in southern India. It is populous but did not top the list in Census 2011.

- Option 3: Delhi - Delhi is the capital city of India and is densely populated with a high growth rate. Despite its large population, it was ranked second in 2011.

- Option 4: Mumbai - Mumbai, the financial center of India, was the most populated metro city in the country according to the Census 2011, with a massive urban population.

- Correct Answer: Option 4 - Mumbai