Is a tweet from donald trump a primary or secondary source?

The oldest seafloor in the atlantic ocean is located closest to the edge of the continents. explain how this age can be used to figure out when north america first began to separate from europe

Why are there restrictions to traveling to cuba?

Why are young eastern european democracies at an increased risk for turmoil during a global recession? a) anger against increased democracy b) failure of the free market system c) government corruption d) lack of from the e. u.