What is known as the series of alliances among european nations in the 19th century, devised to prevent the outbreak of revolutions?

Concert of Europe

Explanation:

The group of European countries that agreed on policies and  formed alliances between 1814 and 1914 to maintain balance of power in Europe and stop the spread of revolutions were known as Concert of Europe.  Its member countries were Austria, United Kingdom, France, France, Italy and Prussia.

It was also known as Congress system because the leaders used to meet and make decisions by mutual agreement. The concert of Europe was founded by United Kingdom, Russia, Prussia and Austria. These members defeated Napoleon and led to the collapse of first french empire. It lasted in two phases the first from 1815 to 1860's and the second phase from 1880's to 1914.

what the first or next guys says

thurgood marshall

explanation: in 1954, thurgood marshall and a team of naacp attorneys won brown v. board of education of topeka, kansas. in this landmark decision, the supreme court held that segregation in public education violated the equal protection clause of the fourteenth amendment.