Final answer:
Adolf Hitler's master race ideology was developed in his manifesto and became government policy in Germany, leading to the persecution of Jews and others. While influenced by practices abroad, the Nazi regime's execution of these ideas was unique to Germany, making it the correct answer to the origins of Hitler's policies.
Step-by-step explanation:
Adolf Hitler's policies for creating a master race were not initially based on the practices of any specific country but were instead formed from his own twisted ideology as presented in his manifesto, Mein Kampf. Within this work, Hitler outlined his beliefs on racial purity and the concept of an Aryan or superior Germanic race, which would guide the treatment of Jews, Roma, and others during the Nazi regime. Hitler also enforced the idea of lebensraum, or 'living space', which justified the expansionist war to create room for the Aryan race.
Although Hitler's ideas were unique to his own cruel vision, it is well-documented that he admired and was somewhat influenced by certain eugenics practices and theories from the United States prior to his rise to power. However, the full implementation and extreme practices of the Nazi regime regarding the master race were largely developed and enacted within Germany itself once Hitler became Chancellor in 1933.
Hence, the correct answer to the given multiple-choice question is 2) Germany, as it is the country where Hitler's policies were fully realized and instituted in a government capacity.