I will give u brainlist What caused the Mongol Empire to break into separate regions ruled by separate leaders?

Cities around the empire split away and became independent nations.
The economy of the empire fell apart due to a lack of trade and business.
A struggle for power among Genghis Khan’s sons and grandsons led to civil war.
Groups throughout the empire built armies and overthrew the Mongols.

How did kennan’s long telegram shape the united states interaction with communism throughout the world? a. the united states sought to restrict the expansion of communism and soviet influence. b. the united states conquered communism by economically oppressing third-world nations. c. the united states created the european union to maintain control of its post-wwii influence. d. the united states sought to extend its influence by militarily forcing democracy on the world.