Final answer:
To smooth dry, flaky skin or calluses on the feet, a foot file should be used, as it is designed to safely exfoliate the skin without harming the surrounding areas. Therefore, the correct option is 2.
Step-by-step explanation:
To smooth dry, flaky skin or calluses on the feet, the best tool to use is a foot file. A curette is typically used for more delicate tasks such as removing earwax or performing certain surgical procedures. A nail rasp is used specifically for nails, while a nail brush is meant for cleaning underneath the nails and not for smoothing calluses. When dealing with calluses, which are areas of thickened skin that form as a response to repeated friction or pressure, a foot file is designed to gently abrade and exfoliate the rougher skin areas without damaging the healthy skin around them.