Question

julie finds a snail on the sidewalk and wants to know whether or not the snail moves throughout the day. she places a single mark on the sidewalk next to the snail.
what will julie use the mark for initially?
○ determining how fast the snail moves
○ acting as a standard unit of measure
○ determining the displacement of the snail
○ acting as a reference point for detecting motion

Explanation:

To detect if the snail moves, a fixed reference is needed. The mark is a stationary point to compare the snail's position against over time. The other options are incorrect: speed requires time/distance measurements, it's not a standard unit, and displacement needs tracking position change from a start point, but the initial purpose is just detecting motion via a reference.

Answer:

acting as a reference point for detecting motion