Final answer:
Fascism is the concept that arose in the 20th century in direct response to the First World War, characterized by extreme nationalism and authoritarian rule. It gained prominence in Italy and Germany, contributing to the rise of totalitarian regimes and the onset of World War II.
Step-by-step explanation:
20th Century Political Ideologies Arising in Response to WWI
The concept that arose in the 20th century in response to the First World War was fascism. Fascism is characterized by extreme nationalism, authoritarian governance, and a disdain for democratic ideals. It emerged mainly during the interwar years, gaining traction in Italy with Benito Mussolini's rise to power and in Germany under Adolf Hitler's rule. This ideology promised to restore national strength and resolve the economic and social crises that Europe faced after the devastation of World War I. Eventually, this led to the rise of totalitarian regimes and contributed to the onset of World War II.
While communism did experience growth in this era, notably with the rise of the Soviet Union after the Russian Revolution during WWI, it does not directly answer the question posed. Since fascism specifically emerged as a direct response in the aftermath of WWI and became identified with the political climate of the interwar period, it is the correct answer to the student's question.