The main idea of the quote is that the Soviets are tightening their contol over Cnetral and Eastern Europe. The other sentences complete that idea by letting us know what they are doing with Central and Eastern Europe.
Answer: Trade made the city-states wealthy. Many were successful and powerful because they specialized and were located in the middle of trade routes. Venice was the most powerful Italian city-state and it specialized in shipping allowing it to control the trade routes in the Mediterranean Sea.
It seemed to underscore basic weaknesses of American educational system
Plessy v. Ferguson set forth the doctrine of "separate but equal" which enabled institutionalized segregation as long as things were "equal"
However, the Court did not define what equal really meant.
So, you might see a bathroom for African-Americans that was a hole in the ground while the whites only bathroom was pristine and modern.
