Answer: I think it might be D.
Explanation:
Answer:
The spectral types and sub-classes represent a temperature sequence, from hotter (O stars) to cooler (M stars), and from hotter (subclass 0) to cooler (subclass 9). The temperature defines the star's "color" and surface brightness. ... Stars are also classified by luminosity class.
Explanation:
The U.S economy produce 20% of the world's output
Physical processes are the natural forces that change earths features.
