The correct answer is B) A graph showing the number of Native Americans between 1492 and 1600.
The most useful in studying the effect of germs exchanged between the New and Old Worlds would be a graph showing the number of Native Americans between 1492 and 1600.
European conquerors introduced diseases for which the Native Americans had no immunity killed thousands. They introduced many diseases unknown for the Native American Tribes. American Indians were healthy and clean people. They took care of themselves and hygiene was important. But when the Europeans arrived, they introduced diseases such as smallpox, measles, chickenpox, Typhus fever, and influenza. These diseases wiped out entire populations.