Is an imaginary "line" from the Earth to the Moon a line, a ray, or a segment? and WHY?

Segment

Step-by-step explanation:

It is a segment because it has two endpoints (the Earth and Moon). If it was a ray, it would go on forever in one direction. It doesn't, so the imaginary line is a segment.  

The first image is a segment, the second is a ray.

Hope this helps. :)

explanation:

previous steps have made pa≅ pb ≅ st ≅ su. setting the compass width to ab allows you to make tu the same length. then δstu ≅ δpab by the sss congruence postulate, and ∠p ≅ ∠s by the reason cpctc.