Correct Response: C. The Hertzsprung-Russell diagram (H-R diagram) is a scatter plot of different types of stars that graphs a star's brightness against its temperature. Brightness is a measure of a star's luminosity and the temperature is dependent on the star's color or spectral class. Both of these characteristics depend on the particular star's composition. With some additional observational data, a star's distance and age (A) and its lifecycle stage (B) can be estimated by analyzing the star's position on the H-R diagram. These properties, however, are not used to plot a star's position on the diagram. The size and composition of a star (D) are also properties that can be estimated using information from the H-R diagram in combination with information from astronomical observations; however, they are not properties used to plot the star's position on the H-R diagram.
