Final answer:
Adolf Hitler based his extremist nationalism on racism, believing in the superiority of the Aryan race and promoting the elimination of other races.
Step-by-step explanation:
Adolf Hitler based his extremist nationalism on racism, as he believed in the superiority of the Aryan race. He propagated the idea that the Aryan race, which he saw as pure and superior, needed to dominate and eliminate other races, particularly Jews.
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