Explanation:

- Speaker: The Speaker of Lok Sabha presides over the sessions and maintains order, but has no authority to sanction spending of public money.

- President: The President of India does give formal assent to the appropriation bill, but this is mainly a constitutional formality after the bill is passed. The President cannot independently sanction expenditure.

- Prime Minister: The Prime Minister leads the government and proposes expenditure through the budget, but cannot directly sanction its utilization.

- Parliament: Parliament has the final authority. No public money can be spent without its approval via the Appropriation Act.

Correct answer: Parliament (Option 4)