Explanation:

- Megasthenes was a Greek historian and diplomat.

- He is best known for his work, "Indica," which provided valuable insights into ancient India.

- ?? Let's explore the options:

1. Alexander:

- Alexander the Great invaded India in 327 BC.

- Megasthenes did not visit India during the time of Alexander.

2. Bindusara:

- Bindusara was the son of Chandragupta Maurya.

- Megasthenes did not visit India during Bindusara's reign.

3. Chandragupta Maurya:

- Megasthenes visited India during his reign.

- He was sent as an ambassador to the Mauryan court by Seleucus I.

4. Ashoka:

- Ashoka was a Mauryan ruler after Chandragupta and Bindusara.

- Megasthenes visited before Ashoka's time.

- The correct answer is option 3: Chandragupta Maurya.

-