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

Julie will use the mark AS A REFERENCE POINT FOR DETECTING MOTION.

We are told in the question that, Julie placed a mark on the sidewalk next to the snail because she wants to know whether the snail move throughout the day or not. Considering the aim of Julie for putting the mark, it is obvious that Julie put that mark in order to monitor the snail's movement. If the snail remain at the same point, that means the snail is not moving. If the snail move, the drawn line will allow Julie to know how far the snail has move. Thus, the drawn line serves as a reference point for Julie.

Julie will use the mark AS A REFERENCE POINT FOR DETECTING MOTION.

We are told in the question that, Julie placed a mark on the sidewalk next to the snail because she wants to know whether the snail move throughout the day or not. Considering the aim of Julie for putting the mark, it is obvious that Julie put that mark in order to monitor the snail's movement. If the snail remain at the same point, that means the snail is not moving. If the snail move, the drawn line will allow Julie to know how far the snail has move. Thus, the drawn line serves as a reference point for Julie.

b. lithosphere, asthenosphere, mesosphere   is the answer most likely

i think the answer is a.keratin is the pigment responsible for skin color.