In the end, what causes the Great War to happen ?

The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary. In June 1914, a Serbian-nationalist terrorist group called the Black Hand sent groups to assassinate the Archduke.

The assassination of Archduke Franz Ferdinand of Austria caused the war

Explanation:

World War I, also known as the Great War, began in 1914 after the assassination of Archduke Franz Ferdinand of Austria. His murder catapulted into a war across Europe that lasted until 1918.

the roman army grew in size and became dominant in the mediterranean region.

just finished this it is b. centrifugal force