Final Answer:
The main cause of World War II was Germany's expansionist policies under Adolf Hitler. Thus option c is correct.
Step-by-step explanation:
Hitler's ambition to establish German dominance over Europe led to aggressive territorial expansion, violating treaties and annexing neighboring countries. Germany's aggressive actions, such as the invasion of Poland in 1939, marked the beginning of the war. Hitler sought to acquire Lebensraum (living space) for the German people, disregarding international agreements and provoking conflict with other nations.
Germany's expansionism was characterized by its territorial ambitions, aiming to regain lost territories from World War I, expand its influence, and impose its ideology across Europe. This expansionist agenda instigated a series of events that ultimately escalated into a global conflict involving major world powers.
The invasion of Poland was a pivotal event triggering the war, but it was a consequence of Germany's broader expansionist goals rather than the sole cause. The Allies' resistance and subsequent involvement were reactions to Germany's aggressive expansion, leading to a prolonged and devastating conflict. Therefore, while the invasion of Poland was a significant event, the root cause and catalyst for World War II lay in Germany's expansionist policies and actions.
Thus option c is correct.