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").
Input: Fact1: All life relies on a relatively narrow range of pH, or acidity., Fact2: Acidity is measured with a pH meter or with pH paper strips., Question: What relies on a relatively narrow range of something you can measure with paper strips? (A) Length (B) voltage (C) all life (D) mammals (E) humans (F) Most plants (G) agriculture (H) animals
Output:
C