Explanation:

- Bindusara was the second Mauryan emperor and famously the father of Ashoka, making him a notable figure in Indian history.

- Ashoka, one of India's greatest rulers, is well-known for spreading Buddhism and for his efforts in unifying the Indian subcontinent through peaceful means.

- Correct Answer: Option 2, Ashoka

- Kanishka, a prominent Kushan emperor, is remembered for his role in spreading Buddhism beyond India but was not related to Bindusara.

- Skandagupta was a Gupta dynasty ruler who defended India against the Huns but was unrelated to Bindusara.

- Harsha Vardhana was a ruler in the 7th century, centuries after Bindusara, and was independent of the Mauryan lineage.