Which of the Following, Along with Warfare, Likely Contributed to the Gradual

Which of the following, along with warfare, likely contributed to the gradual decline of western Europe and the western Mediterranean?

A) a dramatic decrease in population due to a massive number of refugees fleeing Germanic and Hunnic invasions
B) a period of climatic cooling and the outbreak of plague, which killed large numbers of people
C) a blight that destroyed most of Europe's wheat crop and resulted in wide-scale starvation
D) an extended period of drought, which caused large numbers of people to abandon their homes