The correct answer for this question is option 4: they used chariots driven by horses. The Aryans were a nomadic Indo-European people who migrated into the Indian subcontinent around 1500 BCE. They were skilled in warfare and employed advanced military tactics, one of which was the use of chariots driven by horses. This gave them a significant advantage over the pre-Aryans, who did not have access to such advanced technology. The chariots provided the Aryans with mobility and speed on the battlefield, allowing them to swiftly attack and retreat. This tactic proved to be highly successful and enabled the Aryans to conquer and subdue the pre-Aryan civilizations.