The correct option is Rajendra Prasad.
Explanation
The Constituent Assembly of India was constituted in November 1946 under the scheme formulated by the Cabinet Mission Plan. Its primary task was to draft the Constitution for independent India.
Detailed Analysis:
- Dr. Sachchidananda Sinha: During the first meeting of the Constituent Assembly on December 9, 1946, Dr. Sachchidananda Sinha, the oldest member, was elected as the temporary President (following the French practice).
- Dr. Rajendra Prasad: On December 11, 1946, the Assembly elected Dr. Rajendra Prasad as its permanent President. He presided over the sessions of the Constituent Assembly until the Constitution was adopted and signed.
- Dr. B.R. Ambedkar: He served as the Chairman of the Drafting Committee, which was responsible for preparing the draft of the Constitution. He was not the President of the Assembly.
- Jawaharlal Nehru: He moved the historic 'Objectives Resolution' on December 13, 1946, which laid down the fundamentals and philosophy of the constitutional structure.
Key Takeaway:
Dr. Sachchidananda Sinha was the temporary President (Chairman) for the inaugural session, whereas Dr. Rajendra Prasad was the elected President of the Constituent Assembly.