Using a spectrograph...

A.) How can a spectrogrph be used to indicate that the rings of Saturn are not solid?
B.) Astronomers in the 1940's had difficulty measuring the amount of water in the Martian atmosphere spectroscopically, becuase the Earth's atmospheric water got in the way. They could not yet fly above our atmosphere. How could the spectral lines from the two planets be separated, so that accurate measurements can be made?
C.) A distant star yields a spectrum showing two sets of hydrogen spectral lines: a strong red shifted set, and a weaker blue shifted. How might you interpret this observasion?