With a Professional Army of More Than 1

With a professional army of more than 1.5 million men, the Song emperors:

A) Found it easy to dominate the entirety of East and Central Asia.
B) Nevertheless found it difficult to overpower invading nomadic groups.
C) Ruined their economy paying out dividends and retirement benefits to veterans.
D) Expanded into Jin territory and established a new capital at Kaifeng.