Who was the chairman of the drafting committee of the Constitution of India?

B.R. Ambedkar

The correct answer is Option 2 - B.R. Ambedkar

The chairman of the drafting committee of the Constitution of India was Dr. B. R. Ambedkar.
The Drafting Committee was constituted on August 29, 1947, by the Constituent Assembly of India.
The Drafting Committee was chaired by Dr. B. R. Ambedkar, a prominent jurist, social reformer, and the principal architect of the Indian Constitution.

The members of th Drafting Committee were;

Alladi Krishnaswami Ayyar,
N. Gopalaswami
B.R. Ambedkar (Chairman of the drafting committee.)
K.M Munshi
Mohammad Saadulla
B.L. Mitter
D.P. Khaitan

B.L.Mitter resigned due to health issues and was replaced by N Madhav Rau. D.P.Khaitan died in 1948 and was replaced by TT Krishnamachari.