Correct Option
The Constituent Assembly of India was constituted in 1946 under the Cabinet Mission Plan. Its members were indirectly elected by the Provincial Legislative Assemblies through the method of proportional representation by means of a single transferable vote. Therefore, the statement that it was elected by the Provincial Assemblies in 1946 is correct.
Incorrect Options
Option 2: Jawaharlal Nehru and Sardar Vallabhbhai Patel were members of the Constituent Assembly. However, M.A. Jinnah was not a member, as the Muslim League boycotted the Constituent Assembly's formation and proceedings.
Option 3: The first session of the Constituent Assembly of India was held on December 9, 1946. Dr. Sachchidananda Sinha served as the temporary President. Dr. Rajendra Prasad was later elected as the permanent President on December 11, 1946.
Option 4: The Constitution of India was adopted and enacted by the Constituent Assembly on November 26, 1949. It came into full effect on January 26, 1950, which is celebrated as Republic Day. This date was chosen to commemorate the Purna Swaraj Declaration of 1930.