Final answer:
The Central Powers in World War I consisted of Germany, Austria-Hungary, Ottoman Empire, and Bulgaria. They were opposed by the Allied Powers, which originally included the Triple Entente of Great Britain, France, and Russia, and later grew to include other nations such as Italy and the United States.
Step-by-step explanation:
During World War I, the countries that were part of the Central Powers, who fought against the Allied Powers, were Germany, Austria-Hungary, Ottoman Empire, and Bulgaria. This alliance originally opposed the Triple Entente, which consisted of Great Britain, France, and Russia. Over the course of the war, the Allied Powers grew to include other nations like Italy, the United States, and Japan. Notably, Italy was initially aligned with the Central Powers but switched sides to join the Allies in 1915. The Ottoman Empire joined the Central Powers to regain stature and potentially gain territory, and Bulgaria joined in hopes of territorial expansion as well.