How Did the Nature of Armed Forces Change in the Latter

How did the nature of armed forces change in the latter half of the seventeenth century?

A) Gunpowder technologies were used for the first time in field operations.
B) Improvements in artillery made the use of cavalry obsolete.
C) Army officers became obedient to monarchs instead of serving their own interests.
D) The size of armies decreased as they professionalized and became more efficient.