Explanation:

- Option 1: Xi Jinping

Prime Minister Narendra Modi held a second informal summit with Chinese President Xi Jinping in Mamallapuram, Tamil Nadu, in October 2019. This summit aimed to strengthen India-China relations and included cultural exchanges and delegation-level talks.

- Option 2: Mohammed bin Salman Al Saud

Mohammed bin Salman is the Crown Prince of Saudi Arabia. Although India and Saudi Arabia maintain strong diplomatic ties, this option is incorrect for the October 2019 event in Mamallapuram.

- Option 3: Shinzo Abe

Shinzo Abe was the Prime Minister of Japan. India and Japan have a significant relationship, but this summit was not held with him in October 2019.

- Option 4: Vladimir Putin

Vladimir Putin is the President of Russia. While India and Russia share a longstanding partnership, Putin did not attend the informal summit in Mamallapuram in October 2019.