The correct answer is option 4 - They are constitutional bodies. Each of the mentioned bodies - the Supreme Court, Election Commission, UPSC, and Office of CAG - are established by the Constitution of India. They are not advisory bodies (option 1) as they have specific powers and functions assigned to them by law. They are also not controlled by the legislature (option 3) as they operate independently and are meant to act as checks and balances on the executive and legislative branches of the government. Although they are not "extra-constitutional" bodies (option 2) as they are created within the framework of the Constitution itself. Therefore, the most accurate feature common to these bodies is that they are constitutional bodies, designed to uphold the principles of democracy, justice, and accountability in the Indian system of governance.