Explanation:

- Option 1: Ashoka

- Ashoka was an emperor from the Maurya dynasty.

- His reign was much later than the Haryanka dynasty.

- Option 2: Prasenajit

- Prasenajit was a king of the Kosala Kingdom.

- He was not a ruler of Magadha.

- Option 3: Bimbisara

- Bimbisara was indeed the first ruler of Magadha from the Haryanka dynasty.

- He expanded the kingdom and was known for his diplomatic marriage alliances.

- Option 4: Ajatshatru

- Ajatshatru was Bimbisara’s son.

- He was the successor and continued his policies.