Which statement about the sui dynasty is correct? a. it proclaimed islam as the state religion of china in the ninth century. b. it reunited northern and southern china in the sixth century. c. it began building the great wall of china in the third century b. c. d. it fell to the forces of genghis khan in the twelfth century.

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.