Why Is an Absorption Spectrum Especially Useful for Astronomers

Multiple Choice

Why is an absorption spectrum especially useful for astronomers?

A) It has dark lines in it that allow astronomers to determine what elements are in the star
B) It has bright lines in it which allow astronomers to determine how bright the star is
C) It helped astronomers to understand the rainbows we see on Earth after storms
D) It shows that the stars are transparent; we can see right through them
E) An absorption spectrum is not useful to astronomers at all. When they see one, it means they cannot learn anything about the stars that produced the annoying absorption.