The answer is B: international travel
The correct answer is - Kublai Khan promoted religious tolerance and exchanges between Christians, Muslims, Buddhists, and Hindus.
Kublai Khan, and pretty much all the rulers of the Mongol Empire, even though mostly are portrayed as savages and barbarians, were actually one of the most tolerant of all in there time towards the different cultures and religions, and never made problems to the people they were ruling over on this basis. The Mongols can even be seen like globalists, and they encouraged cultural exchange, religious exchange and tolerance, and were trying to create an environment were people from different ethnicity, cultural and religious backgrounds would live in peace and harmony, and through it to create a unified empire.
Ok do it right and you will get it right
