The correct answer is: Mineral A is harder than mineral B.
Based on the given scenario, if mineral A scratches mineral B, it can be inferred that mineral A is harder than mineral B.
To infer which mineral is harder, we can use the Mohs scale of hardness. This scale ranks minerals based on their ability to scratch or be scratched by other minerals. By rubbing the two unknown mineral samples against each other, if mineral A scratches mineral B, we can conclude that mineral A is harder than mineral B. Therefore, the correct inference is that "Mineral A is harder than mineral B."
