Explanation:

- Option 1: Speaker of Lok Sabha

The Speaker has no constitutional role in the emergency proclamation process.

- Option 2: Prime Minister

The President does not act solely on the advice of the Prime Minister for proclamation of an emergency.

- Option 3: Chief Justice of India

The Chief Justice is not involved in the proclamation of an emergency.

- Option 4: Union Cabinet

Correct Answer: The President can proclaim emergency only on the written advice of the Union Cabinet, as per Article 352 of the Indian Constitution. This ensures collective responsibility and prevents misuse by a single individual.