<span>B World War 2 began.</span>
Answer: The stong nationalism of the Serbians.
Explanation: The Serbians were against plans of Austria-Hungary to colonize their land.
The slave trade between Western Africa and the America's reached its peak in
the mid-18th century when it is estimated that over 80,000 Africans annually
crossed the Atlantic to spend the rest of their lives in chains.
<span>By gradually building up the sea power of the US Navy.</span>