Need

which statement about the sui dynasty is correct?

a.
it was the last chinese dynasty to have its imperial capital located at the northern city of chang'an.

b.
it dismantled large portions of the great wall to obtain building materials for a network of canals.

c.
it's first ruler was wendi, who unified northern china and seized control of western regions.

d.
it lasted for more than five hundred years until it was conquered by the forces of attila the hun.