You will be given a definition of a task first, then some input of the task.
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: treating water is used to remove harmful substances before drinking, Fact2: Hydration is maintained by drinking a lot of fluid., Question: What is treating water to remove harmful substances done before? (A) vaporization (B) bacteria (C) evaporation (D) hydration (E) dangerous (F) Frogs (G) Relieve pain (H) a pathogens
Output:
D