Question ID:PT90 S2 Q19 Passage:The differences in distance from Earth between the stars in any one distant galaxy are negligible compared to the vast distance to the galaxy itself. Thus, if two stars are in the same distant galaxy, any significant difference in the apparent brightness of those stars results from differences in how brightly each is actually burning. Therefore, we should be able to determine how a star's relative actual brightness correlates with other characteristics by studying stars in the same distant galaxy. Stem:Which one of the following is an assumption the argument requires? Correct Answer Choice:DChoice A:If two stars are in two different galaxies, it is not possible to determine whether or not they are approximately the same distance from Earth. Choice B:If any two stars are in the same distant galaxy, differences in the elements each is burning will be detectable from Earth. Choice C:The stars in our own galaxy are not all approximately the same distance from Earth. Choice D:There are stars in distant galaxies that have characteristics, other than brightness, discernible from Earth. Choice E:If there are significant differences in how far away two stars are from Earth, then those stars will differ significantly in apparent brightness.