A student is constructing a stream table to investigate how erosion by a meandering stream is affected by the slope of the land. The student uses the equipment shown. What should the student vary for the different trials of the experiment? A) The number of blocks stacked beneath the tray B) The sediment size of sand used in the stream table C) The size of the hole in the bottom of the container of water D) The volume of water that enters the stream table and collects in the bucket