Explanation:

- Rajendra Prasad: He was the first President of India and presided over the Constituent Assembly, but he was not the head of the Drafting Committee.

- C. Rajagopalachari: He was the last Governor-General of India and a notable politician, but had no role in chairing the Drafting Committee.

- Tej Bahadur Sapru: He was a prominent lawyer and politician but did not hold any significant position in the drafting of the Indian Constitution.

- B.R. Ambedkar: Known as the "Father of the Indian Constitution," he was indeed the Chairman of the Drafting Committee. He played a crucial role in framing and drafting the Constitution.