The Primary Geo-Political Difference Between the Northern and the Southern

The primary geo-political difference between the Northern and the Southern Song dynasties can best be described as the

A) Liao Empire dominated the northern half of China under the Northern Song.
B) Jin Empire dominated the western half of China under the Southern Song.
C) Northern Song controlled the Grand Canal while the Southern Song did not.
D) Southern Song controlled the Grand Canal while the Northern Song did not.