The Constituent Assembly was a body of representatives that was elected to draft the Constitution of India. It was formed under the Cabinet Mission Plan in 1946. The Constituent Assembly had the responsibility of framing a Constitution that would establish India as an independent and sovereign nation.

The answer to the question is option 'A', which is 300. Here are some details about the composition of the Constituent Assembly:

1. Formation: The Constituent Assembly was formed in 1946 under the Cabinet Mission Plan. The members of the Assembly were elected by the provincial assemblies and the princely states.

2. Composition: The Constituent Assembly was composed of 299 members initially. However, later, one more member was added, bringing the total to 300. Out of these 300 members, 229 were from the British provinces, 70 were from the princely states, and one was from the Chief Commissioner's Province of Baluchistan.

3. Representation: The members of the Constituent Assembly represented a wide range of political parties, ideologies, and regions. Some of the prominent leaders who were part of the Assembly included Jawaharlal Nehru, Sardar Vallabhbhai Patel, B.R. Ambedkar, Rajendra Prasad, and Maulana Abul Kalam Azad, among others.

4. Functions: The Constituent Assembly had the task of drafting and adopting a Constitution for India. It held its first meeting on December 9, 1946, and its last meeting on January 24, 1950. The Constitution of India was finally adopted on November 26, 1949, and came into effect on January 26, 1950.

In conclusion, the Constituent Assembly of India had a total of 300 members. These members were elected to draft and adopt the Constitution of India, which laid the foundation for India's democratic system and governance.

Before 1947, The constituent Assembly had 389 members. After the process of partition it came down to 299 seats.

Note: There are 299 seats in the Constituent assembly of India. Rajendra Prasad was the first Chairman of the Constituent Assembly.