Answer:
d) Chemical composition of its outer regions
Explanation:
Spectroscopy is the study of spectral lines, it's an important part of studying the chemistry that goes on in stars and interstellar clouds, spectral lines can give relevant information because every atom or molecule gives off light at a specific frequency, thus, astronomers can look for gas containing a particular atom or molecule by tuning the telescope to one of the gas's characteristic frequencies. Therefore, we can know the chemical composition or a star's outer regions analyzing the spectral lines.
Even though the spectral shape of a blackbody continuum depends on the temperature of the object an there's a relationship between an object’s temperature and the peak of its spectrum, we don't consider this answer as correct because we are not measuring spectral lines but the continuum.
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