b. The migration of African Americans and returning African-American veterans had created greater competition for jobs and housing.
Explanation:
The years after WWI saw many people in the country changing residence. Many soldiers and veterans came back home. Many immigrants also arrived to the United States. However, the main movement of people consisted of African Americans who left the rural areas of the South to travel to cities in the North. This was both a consequence of the segregation that existed in the South as well as the better economy of the North. This migration led to increased competition and therefore, racial unrest.
The large stone structures created by the Neolithic Europeans are called the Stonehenge. It was built around 4500 - 4000 years ago. It's a circle of stones also known as the megalithic monument.
