The elements in a star can be determined by analyzing the star's spectrum. Which statement explains why no two elements have the same spectrum? A. Each element has a unique arrangement of electrons. B. No element has more than two electrons in the first shell. C. Atoms of different elements have different masses. D. Atomic nuclei contain no electrons.

The correct option is C.

Because different elements have different masses, they also end up having different number of energy levels. Different elements emit different emission spectra when they are excited because of their unique energy levels. Each emission spectra has different color. Scientists can easily analyze the composition of a matter by analyzing its spectrum.