B. It reunited northern and southern China in the sixth century.
The Sui Dynasty was a relatively short one, it only lasted from 589 AD to 618 AD. Therefore, A. C. and D. are incorrect because the Dynasty was not in power at those times. So, B is correct because it did reunite northern and southern China with its creation in the 6th century.
I think A hope this helps
( ' 3')
Non-flowering plants are divided into two main groups – those that reproduce with dust-like particles called spores and those that use seeds to reproduce. Spore-bearing plants are simple, or primitive, plants, for example mosses and ferns.
It is on the Jewish flag from the country of Israel.