Explanation:

- Option 1: Porus

- Porus was a king in the region of Punjab during Alexander the Great's invasion.

- He is not associated with the patronage of the First Buddhist Council.

- Option 2: Ashoka

- Ashoka was an influential Mauryan emperor known for spreading Buddhism.

- He patronised the Third Buddhist Council, not the first.

- Option 3: Ajatashatru

- Ajatashatru was a king of the Magadha Empire.

- He is noted for patronising the First Buddhist Council after the Buddha's death.

This is the correct answer.

- Option 4: Chandragupta Maurya

- Chandragupta founded the Maurya Empire and later converted to Jainism.

- He is not connected with the First Buddhist Council.