Which of the Following Factors Was Cited as a Contributing

Which of the following factors was cited as a contributing cause to the end of the English feudal system?

A) a labor shortage caused by high mortality due to the "black death"
B) a disruption of transport in England caused by a fear of smallpox
C) a still unidentified disease outbreak that preferentially killed landowners
D) a series of very wet years that promoted increased mosquito numbers, and therefore an epidemic of malaria
E) an outbreak of a serious plant pathogen that caused crops to fail, initiating a famine