Which of the following accurately explains one of the factors that contributed to world war 1

European countries entered into military alliances that required them to protect one another from attacks.

Although no options have been included, it is possible to say that one of the factors that contributed to World War I were the alliances that had been created in the previous years among the various nations of Europe in search of power. For instance, in 1882 Germany made an alliance, known as the Triple Alliance, with Austria-Hungary and Italy, and, by doing so, they all agreed to protect each other from France - although Italy would eventually declare war on Austria-Hungary. Likewise, France and Russia became allies in 1892, and, in 1907, they formed, together with Great Britain, the Triple Entente. Once the war started, other nations, such as Japan, Belgium, Greece and the United States, just to name a few, sided with one of those two coalitions.