The answer to this is Theory (not hypothesis as some may say)
I've always heard it to be a. schools, but I'm not sure if that's the name for the specific situation you described.
Don’t know for sure but get this app called socratic it will help you!
In the period of the Sui Dynasty (581-618 AD), Chang’an before was named Daxing. However, in a later time, the city got new reformations and innovations and was renamed Chang’an by the Tang dynasty administrators which then served as the Tang capital until its collapse in 904 AD.
This ancient imperial capital was the eastern commencement point of the Silk Road. The Silk Road has been of an enormous importance to the trade and cultural exchange to Xi’an (formerly Chang’an) as well as important crossroads for people from entire China, middle east, Rome, and Central Asia. The city thus developed into a hub of diverse ethnic recognition and religious beliefs.
In addition to the above, the tang dynasty manifested a tremendous cultural and religious fluorescence when it grew into a Buddhist learning center and also Taoism, attracting many pilgrims, and other scholars as well as philosophers. This didn’t end only with Buddhism, many other faith denominations emerged such as Nestorian Christianity, Zoroastrianism and Manichaeism, and later Islam.
therefore, the factors that made the tang cipital of Chang'an a center of culture and trade were mainly A and C; It welcomed foreigners and their beliefs, it was located at one end of the silk Road.
