C! He made an alliance with the other Mongol leaders.
Explanation:
After becoming the head of his clan, Genghis Khan forged alliances with other clans, exterminated the existing clan nobility, and overpowered enemy tribes such as the Tatars. In 1206 an assembly of leaders declared him universal emperor (chinggis khān) of the Mongolian steppe. I hope this helps I studied this is 5th grade!
