The executive power of the Union is vested in the:

President

The correct answer is Option 4  - President

The executive power of the Union (i.e., the central government) in India is vested in the President of India, as per Article 53 of the Constitution of India. However, the President exercises this power on the advice of the Council of Ministers headed by the Prime Minister, who is the head of the government. Therefore, in practice, the executive power of the Union is primarily exercised by the Council of Ministers, with the Prime Minister at the helm.