Final answer:
The statement is true. As stars evolve, their temperatures and luminosities change, often resulting in a shift to a different spectral type that corresponds to the star's new characteristics.
Step-by-step explanation:
As stars evolve, their temperature and luminosity indeed change, leading to changes in their spectral type. The spectral classes O, B, A, F, G, K, M, L, T, and Y, which are ordered by decreasing temperature, are defined by specific features in the spectrum that correspond to the surface temperature of the star. For example, O stars with temperatures over 28,000 K display lines of ionized helium and highly ionized atoms of other elements, while A stars with temperatures of about 10,000 K have the strongest hydrogen lines. Throughout a star's life, its temperature, size, and luminosity change for various reasons, such as contraction during the protostar phase or nuclear fuel consumption during the main-sequence phase. Therefore, as a star ages, its position on the Hertzsprung-Russell (H-R) diagram can shift from one spectral class to another.