Answer;
C. .its shape
Step-by-step explanation;
Stars are classified by their spectra (the elements that they absorb) and their temperature. There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M.
The modern classification system is known as the Morgan–Keenan (MK) classification.Each star is assigned a spectral class from the older Harvard spectral classification and a luminosity class using Roman numerals as explained below, forming the star's spectral type.