Q: In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Fact1: measuring the hardness of minerals requires scratching those materials, Fact2: Minerals are classified by their hardness., Question: What must be done to classify minerals? (A) wash them (B) Phylogeny (C) bury them (D) scratch them (E) treatment (F) Cladistics (G) periodic table (H) throw them
A:
D