Why are revolutions a necessary evil in societies and around the world?Need Answer ASAP.!

How do international trade and specialization affect the global economy

What is the columbian exchange? o a. the changes that resulted from europeans settling in the new world b. the relationships that columbus and his men had with the natives they met o c. the ships that columbus bought with money from the king and queen of spain o d. the increase in the number of native american towns in the new world

Where were the main four settlement locations for immigration the united states in 1900?