Dr. B. R. Ambedkar was the Chairman of the Drafting Committee and played a major role in framing the Constitution.
Step 1: Analyze the options.
- (A) Leader of freedom struggle.
- (B) First Prime Minister.
- (C) Correct.
- (D) Known as Iron Man.
Step 2: Conclusion.
Therefore, option (C) is correct.
Final Answer:
\[
\boxed{(C) \, \text{B. R. Ambedkar}}
\]