Answer:
a system of defensive alliances among European states
Step-by-step explanation:
World War I, or the Great War of 1914, began in part because of a system of defensive alliances among European states. In the decades leading up to the war, many European countries had formed alliances with each other for mutual defense and support. These alliances created a complex web of relationships and obligations, and when one country declared war, it often triggered a domino effect as its allies were drawn into the conflict. This is what happened in 1914, when Austria-Hungary declared war on Serbia. Because Russia had an alliance with Serbia, it declared war on Austria-Hungary, which then prompted Germany, Austria-Hungary's ally, to declare war on Russia and its ally, France. This series of events quickly escalated into a full-scale global war. While the other factors you mentioned (rivalry between France and England, a rebellion in Eastern Europe, and African demands for independence) may have contributed to tensions and conflicts leading up to the war, the system of alliances among European states was the main reason for its outbreak.