What is the purpose of a reference point?

A reference point is a place or object used for comparison to determine if something is in motion. An object is in motion if it changes position relative to a reference point.

i think it’s a. this is because if they measured the mass of something with a mass of 150g, then their final answer would have to be approximately 150g. though all of their answers are almost 150, rosa and tran have the closest answers (or the exact answer) to the accurate one.