Motion is defined as a change in an object's position when compared to other objects around it. Mary Ann was watching a slug crawl across the driveway. She saw that a small rock was beside the slug when she first started watching it.
Since a slug moves so slowly, how does Mary Ann know that the slug is actually in motion?
A) She can tell the slug is moving because time has passed.
B) She can tell the slug is moving because she set her watch.
C) She can tell the slug is moving by never taking her eyes off of the slug.
D) She can tell the slug is moving by comparing the change in distance between the rock and the slug.