The correct answer is option C "determine how a star is moving (toward, away, fast, slow)"
Explanation:
All realized components emanate and assimilate specific frequencies of light, which is important for the electromagnetic range. By considering the frequencies of light (as demonstrated by 'lines' inside the electromagnetic range) discharged by an object in space, astronomers can get a scope of information.
One thing they look at is the adjustment in situation of lines in the range from a star this can tell astronomers the distance away the star is, regardless of whether it is moving towards or away from us and how quick it is moving.
