Q:Answer the question based on the following text.  Question:   A piece of sandpaper was rubbed across a glass table, then the sandpaper was rubbed across some gravel. The friction will be greater between the sandpaper and the glass table or or the sandpaper and the gravel.?    Text:  Rougher surfaces have more friction between them than smoother surfaces.
A:
the sandpaper and the gravel.