A.Italy and Austria-Hungary
Explanation:
The Triple Alliance was the name given to the coalition initially integrated by the German Empire and the Austro-Hungarian Empire at the initiative of Chancellor Otto von Bismarck, to which later Italy would be united, although the Russian Empire was invited to be part of it.
On the one hand, Otto Von Bismarck considered his main diplomatic objective to maintain the isolation of France; On the other hand, Italy thought that its adhesion to the Alliance and its association with Germany were the best way to gain access to the rank of great power. Italy was dissatisfied with the French (and later the German) attitude towards its colonial aspirations in Tunisia and the Horn of Africa, and later a problem would be added to the conflicting interests of Trentino domination between Austria-Hungary and Italy.
The three countries agreed to support each other, should they be attacked by France or by Russia. The treaty was reaffirmed several times until 1913, although the Italian position, as it was seen at the beginning of the First World War, was increasingly uncomfortable. Finally, the Kingdom of Italy decided to fight on the side of the allies in 1915, thus breaking this coalition and becoming part of the Triple Entente.
Italy was promised several territories through the London Treaty that were not granted at the Paris conference, which generated a nationalist discontent (which is why Benito Mussolini joined the Axis side in World War II), while the Ottoman Empire joined the central empires. The war ended with the defeat of the Triple Alliance, which dissolved forever
