Explanation:

- Option 1: Royal Challengers Bangalore - This team did not win the Indian Premier League in 2019. They are yet to secure an IPL championship as of 2023.

- Option 2: Mumbai Indians - This is the correct answer. Mumbai Indians won the 2019 IPL tournament. They defeated Chennai Super Kings in a thrilling final match to claim their fourth IPL title.

- Option 3: Chennai Super Kings - Although a strong team with several IPL titles, Chennai Super Kings were the runners-up in 2019, losing to Mumbai Indians in the final.

- Option 4: Kolkata Knight Riders - While successful in past seasons, Kolkata Knight Riders did not reach the final or win the tournament in 2019.