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: treating water is used to remove harmful substances before drinking, Fact2: Ordinary tap water can be full of harmful substances like chlorine, pesticides and heavy metals., Question: What does treating water remove before drinking it? (A) direct damage to the lungs (B) h2o (C) an area swollen with pus (D) chlorine, pesticides, heavy metals (E) molecules (F) vapor (G) Mutagenic chemicals (H) nonliving organic matter
A:
D