Explanation:

All three statements regarding the President of India's pardoning powers under Article 72 of the Constitution are indeed correct:

- Punishment is for an offence against Union Law: The President has the power to grant pardons in cases where the punishment is imposed under a law enacted by the Parliament of India.

- Punishment is by a Military court: The President can pardon convictions made by courts-martial, which are military courts.

- Sentence is a death sentence: The President holds the power to grant clemency in cases where the punishment is a death sentence.

So, the answer is:

- Option 4: All are correct