What effect did the Bubonic Plague, or Black Death, have on the feudal system? Select one:
a. It caused lords and other nobility to think more critically about how they were treating serfs.
b. It killed mostly members of the noble classes, which left peasants without lords or protectors.
c. It led to the development of the medical profession, which challenged the rights of noble to own serfs.
d. It wiped out half the population of Europe, causing a labor shortage that gave serfs and peasants more political power.