Which statement was one of the reasons for the successful invasion of northern India by Muslim rulers in the late 1100s?

1)Hindu princes followed the principle of nonviolence and did not oppose the invading armies.

2)Muslim invaders came to India on the pretext of establishing trade relations and staged coups from within before taking control of northern India.

3)Muslim invaders established alliances with Sikh princes, and their combined military might resulted in the successful invasion of northern India.

4)Hindu princes wasted resources battling one another instead of uniting against a common enemy.