During the 1920s, the palmer raids, immigration quotas, and the trial of sacco and vanzetti resulted from (1) racial prejudice against african americans (2) opposition to the ku klux klan (3) the fear that american values were threatened by radical ideas (4) the need to strengthen national defense

The Palmer rides were rides on radical leftists - regardless of their skin colour. With this information we can reject the first two answers which are connected to racism.

The Sacco and Vanzetti was a trial of two anarchists that the people have found biased:  this shows that the events were motivated by the fear that American values were threatened by radical ideas (such as leftist and anarchist ideas)

Getting elected because not many people were voting