Explanation:

- Option 1: Ram Nath Kovind

- He served as the President of India from July 2017 to July 2022. Presidents usually have a ceremonial role and don't launch government schemes.

- Option 2: Smriti Zubin Irani

- She is an Indian politician and currently a Minister in the Indian government. She has held multiple portfolios but was not involved in launching this scheme.

- Option 3: Narendra Modi

- Correct Answer: The Pradhan Mantri Shram Yogi Mandhan Yojana was launched by Narendra Modi, the Prime Minister of India, in March 2019.

- This scheme provides pension benefits to workers in the unorganized sector.

- Option 4: Arun Jaitley

- He was a senior leader and served as the Finance Minister but did not launch this scheme.