Use the Passage Below to Answer All Parts of the Question

Use the passage below to answer all parts of the question that follows.
"It is now clear that Old World plagues killed at least half the population of the Aztec, Maya, and Inca civilizations shortly before their overthrow. The sheer loss of people was devastating enough . . . but disease was also a political assassination squad, removing kings, generals, and seasoned advisers at the very time they were needed most. . . . The great death raged for more than a century. By 1600, after some twenty waves of pestilence had swept through the Americas, less than a tenth of the original population remained.
Ronald Wright, Stolen Continents: The Americas Through Indian Eyes Since 1492, 1992.
(A) Identify ONE reason the population of the Americas was so vulnerable to Old World plagues.
(B) Identify and compare the impact of ONE plague that was transferred along trade routes in Afro-Eurasia in the period from 1200 to 1450.
(C) Identify and explain at least ONE other factor that contributed to the destruction of the Aztec, Maya, or Inca empires.