(A) allied with Germany.
(B) invaded Sweden.
(C) denounced the United States.
(D) ** signed a peace treaty with Germany.
EXPLANATIONS BELOW
Concept note-1: -The Treaty of Brest-Litovsk (also known as the Treaty of Brest in Russia) was a separate peace treaty signed on 3 March 1918 between Russia and the Central Powers (Germany, Austria-Hungary, Bulgaria, and the Ottoman Empire), that ended Russia’s participation in World War I.
Concept note-2: -Alliances Prior to World War I World War I had two main factions: the Central Powers, which included Germany, Austria-Hungary, Bulgaria and the Ottoman Empire; and the Allies, which included France, Great Britain, Russia, Italy, Japan and later, the United States.
Concept note-3: -Germany has been blamed because she invaded Belgium in August 1914 when Britain had promised to protect Belgium. However, the street celebrations that accompanied the British and French declaration of war gives historians the impression that the move was popular and politicians tend to go with the popular mood.
Concept note-4: -World War I was one of the great watersheds of 20th-century geopolitical history. It led to the fall of four great imperial dynasties (in Germany, Russia, Austria-Hungary, and Turkey), resulted in the Bolshevik Revolution in Russia, and, in its destabilization of European society, laid the groundwork for World War II.
Concept note-5: -It is evident that trench warfare had a profound impact on soldiers during World War I due to the poor weather conditions, infestation of rats, and shell-shock.