What Is One Reason Why the Spanish Civil War Was

What is one reason why the Spanish Civil War was significant?

A) During the conflict, Germany and Italy aided the Spanish Republic, demonstrating that these three governments shared many of the same ways of thinking.
B) During the conflict, the Soviet Union adopted a position of non-intervention and refused to send aid, which surprised its allies.
C) The conflict functioned as a proxy war and testing ground for the opposing forces that would fight in World War II.
D) The conflict showed that all the major Western powers were so distracted by the prospect of World War II that they ignored other wars in Europe.
E) The conflict demonstrated the ultimate fall of right-wing dictators and, as World War II grew more imminent, gave Britain and France hope.