Who/Which of the following is the custodian of the Constitution of India?

(a) The President of India — The President is the constitutional head of the State, but not the final interpreter or guardian of the Constitution. Verdict: Incorrect.

(b) The Prime Minister of India — The Prime Minister heads the executive/government, not the constitutional adjudicatory system. Verdict: Incorrect.

(c) The Lok Sabha Secretariat — It is an administrative body assisting the Lok Sabha; it has no role as custodian of the Constitution. Verdict: Incorrect.

(d) The Supreme Court of India — The Supreme Court is the final interpreter and guardian/custodian of the Constitution through judicial review. Verdict: Correct.