Explanation:

- Correct Answer: Option 3 - Om Birla

- Om Birla is the current Speaker of the Lok Sabha, having assumed office on June 19, 2019. As of January 26, 2021, he holds this position. The Speaker of the Lok Sabha is a crucial role, responsible for maintaining order and decorum in the house.

- Nitin Gadkari (Option 1)

- A senior leader in the Bharatiya Janata Party (BJP), Nitin Gadkari serves as the Minister for Road Transport and Highways. He has never served as the Speaker of the Lok Sabha.

- Rajnath Singh (Option 2)

- Serving as the Minister of Defence, Rajnath Singh is a prominent BJP leader. He is a former President of the BJP but has not been the Speaker of the Lok Sabha.

- JP Nadda (Option 4)

- JP Nadda is the current President of the Bharatiya Janata Party (BJP), taking office in January 2020. Like Gadkari and Singh, he has never held the position of Lok Sabha Speaker.