Detailed Instructions: 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").
Q: Fact1: measuring the hardness of minerals requires scratching those materials, Fact2: Travel is required as necessary., Question: What is necessary to measure the hardness of materials? (A) treatment (B) tapping (C) rubbing (D) tasting (E) lamphreys (F) scratching (G) strength (H) potassium
A:
F