Answer:
Genghis Khan united the tribes of Mongolia.
Step-by-step explanation:
He was the founder and first Great Khan of the Mongol Empire. He got to power by uniting the nomadic tribes of Northeast Asia. After he found the empire he conquered most of Eurasia. After his death, the Mongol Empire was the largest contiguous empire in history.
The option that said that he founded the Yuan Dynasty could be mistaken because the dynasty was established by his grandson Kublai Khan, but he placed Genghis on the imperial records as the official founder of the dynasty as Taizu.
I hope this answer helps you.