Answer:
D. to unite the Chinese people
Step-by-step explanation:
Before the creation of paper currency, Chinese people conducted their business through a barter system. To obtain a certain good from another people, a person need to exchange with another good that he own.
This system is really problematic because different regions in China used different methods to give valuation toward a certain product. In the end, many people did not want to trade with people who lived in another region because they feared that the goods that they obtain wouldn't have a fair value than they've exchanged.
The creation of paper currency made the valuation of a product became universally accepted in all region.
This made people from different regions interact with each other more and gradually united Chinese people simply through social interactions between them.