Answer:
The main four factors of WWI were alliances, imperialism, militarism, and nationalism, and the one that could most likely lead to war today is imperialism.
Step-by-step explanation:
All powerful states throughout history have engaged in imperialism, from the Roman Empire itself, to the European empires of the modern era, to Imperial Japan and Nazi Germany.
This naturally creates tensions, conflicts and war, not only between the imperialist state and the overridden countries, but also between the different empires coexisting at the same time. One example is WWII in the Eastern Front, in which two imperialist countries: Nazi Germany, and the Soviet Union, were embroiled in one of the deadliest conflicts in history.
For this reason, contemporary imperialism of countries like Russia, China or the United States could lead to a new war. Hopefully, world leaders continue to study the past, and develop conflict solution mechanisms in order to avoid a new war..