3. In response to ongoing invasions into the Byzantine Empire during the sixth and seventh centuries, Emperor Heraclius reorganized the military by OA. creating the theme system
OB. recruiting farmers into the military
OC. collecting higher taxes
OD. requiring military service from all men in the empire.

Which of these would be most useful in studying the effect of germs exchanged between the new and old worlds? a. a graph showing the number of europeans between 1492 and 1600. b. a graph showing the number of native americans between 1492 and 1600. c. a primary source description of the symptoms of an unknown disease affecting native americans in 1492. o d. a primary source description of the symptoms of an unknown disease affecting europeans in 1492.