Well the 15th Amendment was one of the methods used, as well as poll taxes, registration, literacy tests and the grandfather clause. So, if your question has options to choose from, just eliminate these. ☺
Specialization makes us more efficient because because the labor focuses on making only 1 or 2 parts which makes it easier and faster for them to do, it also helps the companies use less resources since they're making the same product.
The British recognised the independence of the United States.
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It increased the amount of war and infighting in west Africa and depleted African resources.