Soil is classified by particle size into one of three different categories: sand, silt, or clay. The diagram shows a comparison of these three particles, as well as a piece of gravel to show size differences. Which best explains why all soil particles are not the same size?

Because they are made upf of different types of dit and rock. there location may affect this as well. if one was in a cave they might be larger. and a water source, like a lake, or rivier, they might be smaller. this is why usually around the bottom of lakes and oceans, you would find sand, not boulders.