D. They felt that the war was none of their business.
Americans during World War I believed the US should stay out of European affairs.
The US believed European wars should be handled by themselves. There was a fear that the war would impact Americans if they were to get involved at all. With so many new immigrants in the country, there was also a fear that a European conflict would split the American people. Neither side would have been a good option for the whole country unless a unifying event took place.