Explain types of policy making​

When and why did the united states enter world war 2

The national security act of 1947 reflected:

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