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: friction causes an object to lose energy, Fact2: Friction occurs when surfaces rub together., Question: what causes an object to lose energy? (A) high temperature (B) electron transport (C) degrees celcius (D) surfaces rubbing together (E) heat is produced (F) degrees Celsius (G) depress neuronal excitability (H) a tree falling
A:
D