Explanation:

- The Indian Agriculture Research Institute (IARI) is a key player in the success of the Green Revolution in India. It played a central role by developing new crop varieties and advanced agricultural practices.

- Option 1: Mumbai

- Mumbai is a major city known for its financial and cultural activities, not primarily for agricultural research.

- Option 2: Ludhiana

- Ludhiana is known for its agricultural contribution, particularly through Punjab Agricultural University. However, it is not the location of IARI.

- Option 3: New Delhi

- New Delhi is indeed the location of the Indian Agriculture Research Institute. It serves as a leading institution in agriculture research and education in India.

- Option 4: Patna

- Patna is another significant city but does not host IARI.