Compare the hardness of gypsum to an everyday substance. (site 3)

Hardness is the opposition that materials offer to alterations such as penetration, abrasion, scratching, shearing, and permanent deformations among others. During the course of history, during the study and classification of minerals, there was a moment when it became pertinent to establish a method that would allow to discern the different degrees of hardness of rocks and minerals.

The answer to this is the 3rd choice!