Explanation:

- Option 1: Jawaharlal Nehru was India’s first Prime Minister and served from 1947 to 1964. He held office for about 17 years, making him the longest serving Prime Minister of India as of April 2021.

- Option 2: Indira Gandhi, his daughter, served two non-consecutive terms (1966–1977, 1980–1984), totaling around 15 years.

- Option 3: I. K. Gujral was Prime Minister for less than a year (1997–1998).

- Option 4: Narendra Modi became PM in 2014 and, as of April 2021, completed around 7 years.