Which of the following would most historians consider the best explanation for the rapid changes depicted in the chart shown above?

(A) The global movement of peoples, enabled by industrial-era transportation (B) The eradication of major famines by improvements in agricultural science (C) The decreased impact that modern wars have had on civilian populations (D) The effect of modern medical innovations and increased access to vaccinesExplanation: (D) This question tests use of evidence and historical interpretation, as well as causation. Answer A has little to do with population growth, while the steadily increasing impact of war on civilian populations makes C false. Answers B and D are commonly given as reasons for population growth, but most historians favor medical improvements as a prime cause.