How could one act of terror cause a world war?

'How could one act of terror cause a world war? Explain the causes behind World War I and what might have been done to prevent it
1914, World War One began, the most horrific war the human race had ever seen, lasting for 4 years and precisely three months. Estimates of just over 30 million people were killed. Those who lived through this war referred to it as the 'Great War', we as a country lost just fewer than sixty two thousand lives. But what lit the fuse, what event sparked the domino styled war which inturn took so many innocent lives? And more importantly, who was responsib…