How have the barriers to migration changed over time?

Renewable resources of west and central africa include:

The formation of the planet uranus is estimated to have occurred approximately when?

What statement about the economy of france is not true? a. paris is a major manufacturing center b. marseille is a busy seaport on the mediterranean coast c. farming is the major activity in the alps. d. world-famous wines are produced in the bordeaux region c. farming is the major activity in the alps