Which of the following nations was a member of the "Concert of Europe"?

The United Kingdom, Austria, Russia, and Prussia were all members of the " Concert of Europe"

"Concert of Europe" was created November 20, 1815 by Great Britain, Russia, Austria, (from 1867 as Austro-Hungary), Prussia (1871 as Germany). In 1818 joined by France, in 1867, also Italy. In the event of war countries have set a common policy which aims to preserve the European balance so that no state rise to the hegemony. The final agreement put an end to the outbreak of World War I in 1914. But already there was internal division into two antagonistic blocs of countries: the Triple Alliance (1882; Germany, Austria-Hungary, Italy) and the Triple Entente (1907, United Kingdom, France, Russia)