What are these degrees vary, but are all specific to a certain specialized occupation; ex: dentist, architect ? What is a four-year post secondary school, in which you focus on a major of study

I need specific answers

https://www.nap.edu/read/5129/chapter/5

the mongolian invasion of china and central asia resulted in a disruption of the silk road as the chinese garrisons lost support from the chinese kingdoms which fell under the mongols. however, as the mongols established a formal dynasty in china, the successors of genghis khan restored the garrisons along the silk road allowing the safe travel caravans again.

jewish people, gypsies, and political opponents.