What was a shared reason why austria-hungary and germany became members of the triple alliance?

In my opinion

World War I is the climax of all the contradictions that exist in European countries. Before the outbreak of World War I the situation in the European region had heated up, there had been competition between countries in Europe. At that time Europe was divided into two rival camps. The existence of a Triple Agreement from France et al and the Triple Alliance from Germany et al. With the breakup of two camps, from 1908, several crises had tested competing alliances, pushing Europe closer to the War. Specifically, the Bosnian event involved Russia, Austria-Hungary, and Serbia. This incident contained a lot of material which eventually waged a war in 1914.

In my opinion

World War I is the climax of all the contradictions that exist in European countries. Before the outbreak of World War I the situation in the European region had heated up, there had been competition between countries in Europe. At that time Europe was divided into two rival camps. The existence of a Triple Agreement from France et al and the Triple Alliance from Germany et al. With the breakup of two camps, from 1908, several crises had tested competing alliances, pushing Europe closer to the War. Specifically, the Bosnian event involved Russia, Austria-Hungary, and Serbia. This incident contained a lot of material which eventually waged a war in 1914.

Explanation:

do you have a list of sources to choose from?