Final answer:
Option (d), The Spanish Civil War served as a 'dress rehearsal' for World War II, with Hitler and Mussolini supporting Franco's forces and ultimately leading to the establishment of a fascist regime in Spain.
Step-by-step explanation:
The Spanish Civil War is an important event in the larger context of world history because it acted as a "dress rehearsal" for World War II. During the conflict, both Adolf Hitler and Benito Mussolini provided support to Francisco Franco's Nationalist forces, allowing them to test their military strategies and equipment.
Conversely, while the Soviet Union supported the Republican side, the major European powers and the United States adopted a policy of nonintervention. The war ended with Franco establishing a fascist regime, which did not directly align with Germany or Italy in World War II, but the support from Hitler did strengthen the relationship between these fascist powers.