The Primary Geopolitical Difference Between the Northern and the Southern

The primary geopolitical difference between the Northern and the Southern Song dynasties can best be described as (Map 8-3, p. 203)

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