Respuesta :
The single mark placed on the sidewalk by Julie has been acting as the reference point for detecting the motion of the snail. Thus, option D is correct.
The snail has been the shelled animal that has been mostly residing in the resting condition with limited movement. To evaluate the movement of the snail, there has been the consideration of a point that was the starting point from the movement.
The line that has been set across the sidewalk has been acting as the reference, and the distance traveled has been calculated from that point. Thus, option D is correct.
For more information about the reference point, refer to the link:
https://brainly.com/question/1674904