Explain the geographic context for the historical development/event shown in this 1946 cartoon ?

Aside from low birthrates and high death rates, what can cause a country’s population to decline

The answer because i don’t know it someone

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.