According to economist Julian Simon, O A. legal immigrants have a favorable impact on the welfare of American citizens, but illegal immigrants have a negative impact. However, the positive effect of the legal immigrants is stronger than the negative impact of the illegal immigrants. O B. legal and illegal immigrants have a positive effect on the welfare of American citizens. O C. legal immigrants have a favorable impact on the welfare of American citizens, but illegal immigrants have a negative impact that almost exactly offsets the positive effect of the legal immigrants. O D. legal and illegal immigrants have a negative effect on the welfare of American citizens