It Was More Difficult for Serfs to Improve Their Economic

It was more difficult for serfs to improve their economic and social status because:

A) serfs were forced to work every daylight hour of every day to produce food for their lord.
B) serfs were illiterate,and literacy was required for social and economic mobility.
C) serfs were regularly fined large amounts by their lords for very small infractions.
D) serfs were tied to their lord's manorial lands and so could not move.
E) the aristocracy violently oppressed all serfs.