Explanation:

- Option 1: Dr. B.R. Ambedkar

- Dr. B.R. Ambedkar is widely regarded as the Father of the Indian Constitution.

- He was the Chairman of the Drafting Committee.

- Ambedkar played a key role in shaping and framing the Constitution of India.

- Option 2: Mahatma Gandhi

- Known as the Father of the Nation for his role in the independence movement.

- He was not directly involved in the drafting of the Constitution.

- Option 3: Jawaharlal Nehru

- The first Prime Minister of India.

- Contributed to the constitutional process but not the primary architect.

- Option 4: Vallabhbhai Patel

- Known as the Iron Man of India.

- Played a significant role in integrating princely states but not in drafting the Constitution.