How did the cavalry change during the feudal era?

How did the cavalry change during the feudal era?
 
  A) Prior to feudal society the cavalry was light armored. With the advent of feudal society there was a shift to heavy armored cavalry as modeled in the East.
  B) The invention of stirrups aided the heavily cavalry in control and execution and heavy cavalry became the main strike force of armies.
  C) The feudal cavalry shifted from heavy armored to light armored for maneuverability and speed.
  D) Light armored was introduced with the stirrup to Europe as a viable cavalry tactic in the Middle Ages.
  E) None of these