Explanation:

- Under Article 352 of the Indian Constitution, the President of India can declare a National Emergency.

- This declaration is made based on the written advice of the Union Cabinet.

- The "Cabinet" includes only the Prime Minister and senior-most Ministers, not the entire Council of Ministers.

- The Chief Ministers of states do not have any formal role in this process.

- The Prime Minister alone cannot advise the President—it's a collective decision of the Cabinet.

- The Council of Ministers is a broader group, which also includes Ministers of State and Deputy Ministers, but the Article specifically refers to the Cabinet.

Option:3 - Cabinet is correct.