Rafael lives near a road at the bottom of a hill. His parents are concerned that soil will wash off the hill and rocks will fall onto the road. Rafael conducts an investigation to find out if grass
growing on a hillside will help stop soil erosion. He collects two samples of the same size and
type of soil. One sample of soil has grass growing on it and the other does not. He places
each sample of soil in a small tray. After pouring the water onto both pieces of soil, Rafael
makes an observation. The water collected in the tray under the soil with grass looks clearer
than the water collected in the tray under the soil without grass. What conclusion can Rafael
make from his observation? (6.E.2.4)
The soil without grass was loose, so more water stayed in the soil.
The grass helped to move the water through the soil.
The soil without grass was sticky, so more water stayed in the soil.
The grass helped to hold the soil in place.