During the middle ages, rats that were covered with fleas held deadly germs and were imported into europe with trade goods. the fleas would jump off of the rat and bite humans, and they would become infected and fall terribly ill. the symptoms included high fever, vomiting, chills, swelling, diarrhea, and deliriousness. it spread easily and rapidly. the black death did not reach north or south america, but historians believe between 50 to over 100 million men, women, and children may have died to this terrible disease.

a.
comparison/contrast

b.
cause/effect

c.
sequence

d.
classification