B. By stirring up anti-foreign feelings.
Step-by-step explanation:
After World War I, a lot of people started to have negative feelings towards foreigners and immigrants, as they did not want to become involved with other countries whatsoever.
The Ku Klux Klan was originally created to harm African Americans. This was prominent in the South, as many former Confederates were angry that African Americans were gaining rights. After World War I, this hate started to not only stay with African Americans but also went to immigrants and even women in some cases.
A lot of the United States believed in isolationism, which is where the country does not get involved in foreign problems and affairs. This is the main reason why the United States did not join the League of Nations, they did not want to get involved in the problems of other countries and definitely did not want to get caught up in another war. This "isolationist" attitude would sometimes turn into hate for immigrants, which can be seen with the Ku Klux Klan.