What materials are sand, quartz crystals, and plastic beads used for in manicuring?

The correct choice is that sand, quartz crystals, and plastic beads are used as agents for scrubs. These materials are commonly incorporated into exfoliating scrubs, which help to remove dead skin cells and smooth the surface of the skin. This is particularly beneficial in the context of manicuring, where maintaining healthy and smooth hands and nails is important. The texture of these materials provides an effective way to achieve gentle exfoliation, leading to softer skin and better overall nail care.

While the other options suggest alternative uses for these materials, they are less accurate in this context. For instance, filing nails typically involves tools like emery boards or nail files, not sand or beads. Creating nail art is usually done with polishes, stickers, or gels designed specifically for that purpose. Nourishing cuticles generally requires oils or creams that are rich in vitamins and hydration, rather than abrasive materials. Thus, the use of sand, quartz, and plastic beads aligns most closely with the role of scrubs in the manicuring process.