How Did the Battle of Legnano Mark a Military Milestone

How did the Battle of Legnano mark a military milestone?

A) A feudal cavalry of armed knights was decisively defeated by an army composed primarily of infantry from the cities.
B) Gunpowder technologies were used in Western warfare to decisive advantage.
C) The long bow altered the intimacy of warfare by permitting warfare to occur at great distances.
D) A feudal cavalry coordinated its attack with naval forces in order to attack from land and sea simultaneously.