Final answer:
A statement identifying unknown elements that make up a star refers to the star's composition, predominantly hydrogen and helium, with variations in the abundance of heavier elements ('metals'). The star's metallicity measures the fraction of its mass composed of these heavy elements.
Step-by-step explanation:
A statement identifying unknown elements that make up a star represents the star's composition. The determination of a star's composition is derived from the analysis of its detailed spectrum. The majority of stars, including the Sun, consist mostly of hydrogen and helium. However, there is a variation in the abundance of heavier elements, which are referred to as 'metals'. Stars like the Sun, which are population I stars, tend to have these heavy elements making up about 1-4% of their total mass. On the other hand, population II stars, which are older and found in the outer galactic halo and globular clusters, have much lower concentrations of these heavy elements. The metallicity of a star indicates the fraction of a star's mass that is composed of heavy elements. For instance, the Sun has a metallicity of 0.02, implying that 2% of its mass is made of elements heavier than helium.