Explanation:

- Mihirakula: A Hunnic ruler, known for his conquests in Northern India. However, there are no historical records indicating he cut down the Bodhi tree.

- Pushyamitra Sungha: Founder of the Shunga dynasty. He is sometimes alleged to have persecuted Buddhists, but there's no definitive evidence he targeted the Bodhi tree.

- Shashanka: He was the king of Gauda in ancient Bengal. Historical texts suggest he is responsible for cutting down the Bodhi tree.

- Turks: This refers to various Turkic invasions in India. They played no known role in the destruction of the Bodhi tree.

Based on historical texts, the correct answer is:

Option 3: Shashanka