What type of material should be used as an abrasive in sandpapers?

The use of "grit" as an abrasive material in sandpapers is the best choice because grit refers to the size and composition of the abrasive particles used on the sandpaper. Grit sizes are categorized numerically, where lower numbers indicate coarser abrasives and higher numbers indicate finer abrasives. This designation allows users to select sandpaper suited for specific tasks, whether rough sanding or smoothing surfaces.

While quartz is indeed a common abrasive used in some types of sandpaper, it is not the term that encompasses the full range of abrasive options found on sandpapers. Pumice can also be an abrasive material, particularly in special applications, but it is not as universally applicable as grit. Clay, on the other hand, is not suitable as an abrasive; it is more often associated with filler materials or bonding agents in sandpaper production rather than as an abrasive itself. Thus, the term "grit" appropriately encompasses the variety and functionality of abrasive materials utilized in sandpapers, making it the correct choice.