The correct answer to this question is D) they comprised a large part of the membership of the Ku Klux Klan.
The characteristic that was true about the native-born Protestants was that they comprised a large part of the membership of the Ku Klux Klan.
The Ku Klux Klan was founded in 1886 and was an organization formed by white men that opposed the ideas of Reconstruction of Republican members and the equality in economy and politics between whites and African Americans. The Klan mostly operated in the Southern states of the U.S. and one characteristic of its members was that they were native-born Protestants that comprised a large part of the membership of the Ku Klux Klan.