Teacher:In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").
Teacher: Now, understand the problem? Solve this instance: If one mineral can scratch another mineral then that other mineral is softer than that one mineral, as can be tested with (A) a diamond and steel (B) a rock and glass (C) a diamond and agate (D) a ruby and salt
Student:
C