Because dark line spectra result from passing white light through ionized gasses and plasmas, which is what the atmosphere of stars are made of. These frequencies are scattered by the star's atmosphere as it leaves the surface (photosphere) of the star, and don't make it to earth.
The question is concerned with the regions found within California, which are the Coastal Region, Mountain Region, Central Valley Region, and the Desert Region.
The Coastal Region is located furthest to the west out of all of these regions. The Coastal Region is where the California meets the Pacific Ocean, and it has a somewhat moderate and constant climate throughout the year due to its location near the ocean.
The material that makes up the medium such as air or water and the temperature.
What is Pluto is changing exactly <span />
