The correct answer is option 3: The People of India. The source of authority of the Indian Constitution is the people of India because they are the ones who have given their consent and have adopted the Constitution. The Constitution is a document that lays down the fundamental rights, principles, and guidelines for the governance of the country. It was drafted by a Constituent Assembly, which consisted of representatives elected by the people of India. The Constitution provides for a democratic system of government where the power ultimately lies with the people. The elected representatives are entrusted with the responsibility to govern on behalf of the people and to ensure that the principles and provisions of the Constitution are upheld. Thus, the source of authority for the Indian Constitution is the people of India themselves.