The Chairman of the constituent Assembly was _______
(A) Jawaharlal Nehru
(B) Jai Prakash Narayan
(C) C Rajgopalchari
(D) Dr Rajendra Prasad

Hint:
The constitution of India was a supreme body, which was formed on the recommendation of the Cabinet Mission which visited India in 1946. The Cabinet Mission provided a framework and on the basis of framework, a Constituent Assembly was constituted on 9th December, 1946.

Complete answer:
The Constituted Assembly was formed on 9th December, 1946. The Constitution body was elected by the Provincial Legislative Assembly having 389 members which included 93 from Princely States and 296 from British India.
The seats allotted to the British Indian provinces and princely states were allotted in proportion to their respective population and were divided among Muslims, Sikhs and the rest of the communities.
The first meeting of the Constituent Assembly took place on 9th December, 1946 at New Delhi, On 11th December, 1946 , the Chairman of the Constituent Assembly was elected; Dr. Rajendra Prasad

Functions of the Constituent Assembly:
1) Frame the Constitution.
2) Pass laws and involvement in the decision making process.
3) Elected Dr. Rajendra Prasad as the first president of India.
4) On 24th January, 1950 the National Anthem was adopted.
5) The Constituent Assembly existed for approx. three years, and the last session was held on 24th January 1950.

Note:
The first meeting of the Constituent Assembly took place on 9th December, 1946 at New Delhi, On 11th December, 1946 , Dr. Rajendra Prasad was elected as the Chairman of the Constituent Assembly. The Constituent Assembly existed for approx. three years.

So, the correct answer is an option(D) Dr. Rajendra Prasad.
The Chairman of the constituent Assembly was Dr. Rajendra Prasad.