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 less between the sandpaper and the glass table or or the sandpaper and the gravel.? 

