The Architect of the Indian Constitution is B.R. Ambedkar, as mentioned in option 2. Ambedkar played a key role in drafting the Constitution of India after India gained independence from British rule in 1947. He was appointed as the Chairman of the drafting committee and was responsible for shaping the fundamental principles and laws of the Constitution. Ambedkar was a highly educated and respected leader who dedicated his life to the upliftment of marginalized communities. His keen understanding of social issues and commitment to equality and justice made him the perfect choice for this important task. It is worth noting that while other leaders such as Mahatma Gandhi, Jawaharlal Nehru, and B.N. Rao played significant roles in the Indian freedom struggle and nation-building, Ambedkar`s expertise in law and social justice made him the primary architect of the Indian Constitution.