Answer:
Imperialism: The policy of extending a nation's authority by territorial acquisition or military presence. This contributed to the coming of WWI by leading to a competition among European nations to compete for overseas colonies and increased tensions between countries due to conflicting claims to territories. A historic example of this is the Scramble for Africa, where the major European powers competed for control over African territories.
Nationalism: A feeling of devotion to one's nation and the desire for it to flourish. This contributed to the coming of WWI by creating a sense of superiority among people in a certain nation, motivating them to fight for their nation’s interests against other countries. An example of this is Germany's increasing sense of nationalism and desire to become a great power during the late 19th century.
The Alliance System: A set of treaties between countries in order to ensure mutual defense and protection. This contributed to the coming of WWI by making it difficult to resolve international disputes without escalating into war due to the obligation for states to honor the alliances they had formed. An example of this is the Triple Entente, which was signed between Britain, France and Russia in 1907, which forced Germany to fight a two-front war in WWI.
Militarism: A policy of maintaining strong armed forces and being prepared to use them aggressively to defend or promote national interests. This contributed to the coming of WWI by leading to an arms race between the major European powers and encouraging governments to view military means as a legitimate and effective solution to international disputes. An example of this is Germany's adoption of unrestricted submarine warfare as a way to secure victory in the war.
The specific event that sparked WWI was the assassination of Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, and his wife Sophie by Gavrilo Princip on June 28, 1914. This event caused the world to hurtle towards war as it led to Austria-Hungary declaring war against Serbia and its allies. This in turn triggered the previously formed alliances between major European powers, causing them to enter into war with each other in a matter of weeks.