How did western industrial powers gain global empires?

Describe how the ways in which african americans migrated during the great migration were similar to the immigrants who arrived from other countries in the early 1900s.

The information box says that the han added 4,000 miles of wall. refer to the mileage scale. how can this be true?

The law of increasing costs states that as a country produces less of one product and more of another, there is an increase in the resources needed to expand production of the second product.