The correct answer is option 'B', Sachchidanand Sinha.

Explanation:

The Constituent Assembly of India was formed to draft the Indian Constitution after India gained independence from British rule. The first meeting of the Constituent Assembly was held on December 9, 1946, in the Constitution Hall, New Delhi. The primary task of this meeting was to elect the interim President of the Constituent Assembly.

Sachchidanand Sinha, a prominent leader and politician, was chosen as the interim President in the first meeting of the Constituent Assembly. Sinha was a respected figure in Indian politics and had played a significant role in the freedom struggle. He was one of the founding members of the Indian National Congress and had actively participated in various movements against British rule.

Sinha's election as the interim President of the Constituent Assembly was a unanimous decision made by the members present in the meeting. His selection was seen as a mark of respect for his contribution to the freedom struggle and his integrity as a leader.

As the interim President, Sachchidanand Sinha presided over the proceedings of the Constituent Assembly until the election of Dr. Rajendra Prasad as the permanent President on January 11, 1950. During his tenure, Sinha played a vital role in ensuring smooth functioning and guiding the assembly towards the drafting of the Indian Constitution.

It is worth mentioning that Pandit Jawaharlal Nehru, who later became the first Prime Minister of independent India, was also a member of the Constituent Assembly. However, he was not chosen as the interim President in the first meeting. Nehru's leadership and contribution to the nation were acknowledged in different capacities, but the responsibility of leading the Constituent Assembly initially fell on Sachchidanand Sinha.

Sachchidanada sinha is oldest member of indian Constitutional assembly later gives to president to rajendra prasad