Question

fill in the blank question
you can tell that the boat is in motion using the

as a reference point because the distance between the two objects changes
need help? review these concept resources.
read about the concept

Explanation:

In physics (a subfield of Natural Science), to determine if an object (the boat) is in motion, we use a reference point. Common reference points for a boat could be a stationary object like a tree, a dock, or the shore (since the distance between the boat and these stationary objects changes as the boat moves). Assuming a typical scenario, a stationary object like the shore (or a tree, dock, etc.) is used. For the sake of a common answer, "shore" (or other stationary objects like "tree", "dock") is appropriate as the reference point because the distance between the boat and the shore changes when the boat moves.

Answer:

shore (or tree, dock, etc. - any stationary object relative to the boat's movement)