Lexington and Concord, Massachusetts on 19 April 1775
The Columbian exchange was the arrival of new species in the Old and the New Worlds. Among the many species that arrived in the New World were the bacteria and viruses that were causing many illnesses but to which the Old World people were immune. The Native Americans were not immune so many of them, by some estimates even 90 %, died.
I think that the best answer is "nation" but sometimes the word "nation"also refers to people without recognised borders, such as the Kurdish people or Jews before the establishment of modern Israel.
I think option 4, to explain where black holes are located
Donald trump according to the year of 2017
