The composition of a star is determined from the red or blue shift of spectral lines in a spectrum, the width of the spectral lines in the spectrum.
The study of light and other radiation absorption and emission by matter is called spectroscopy. Electromagnetic radiation into its constituent wavelengths, in a spectrum, just like a prism splits light into a rainbow of colors.
The composition of a star is determined from the red or blue shift of spectral lines in a spectrum, the width of the spectral lines in the spectrum.
Hence, option D is correct.
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