Q:Read the passage below and choose the right answer to the following question (choices are the sandpaper and the glass table or or the sandpaper and the gravel. ):  Rougher surfaces have more friction between them than smoother surfaces.   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.?
A:
the sandpaper and the gravel.