Answer: D. Favoring the rich and powerful of each territory he conquered
Step-by-step explanation:
Genghis Khan forged one of the largest empires to ever exist on Earth and he did this primarily by having a strong army. When it came to uniting the empire however, a strong army could not always be used so he had other strategies as well.
Some of those included giving promotions based on merit instead of relationships and status which ensured that the empire was administered well. He incorporated the people he conquered into the empire and dispossess the leaders of conquered clans often giving it to his soldier as spoils of war.
He did not favor the rich and powerful in his conquered territories however, taking their wealth for himself, soldiers and the empire in most cases.