Final answer:
The complete stellar classification system categorizes stars based on surface temperature, indicated by spectral classes, and luminosity class, which reflects their size and brightness.option a is correct.
Step-by-step explanation:
The complete stellar classification system uses two primary characteristics to categorize stars: surface temperature and luminosity class. The surface temperature is represented by a star's spectral class, which is categorized into types O, B, A, F, G, K, M, L, T, and Y, with each class being further subdivided into subclasses numbered from 0 to 9. The luminosity class, on the other hand, indicates the size and brightness of a star and falls into different categories, such as main-sequence stars, giant stars, or supergiant stars, as can be seen on the Hertzsprung-Russell diagram.
These classes are distinguished by studying the subtle differences in a star's spectrum. For example, our Sun is classified as a G2 V, indicating it is a main-sequence star with a surface temperature corresponding to the spectral class G2.The complete stellar classification system categorizes stars based on surface temperature, indicated by spectral classes, and luminosity class, which reflects their size and brightness.