Answer : 2. "कैबिनेट मिशन योजना, 1946 "
Explanation :

The Constituent Assembly of India was constituted based on the Cabinet Mission Plan of 1946. The plan was proposed by the British government and aimed at devising a constitutional framework for India's independence. It laid the foundation for the formation of the Constituent Assembly, which played a crucial role in drafting the Constitution of India, ultimately leading to India's independence in 1947.