Q: 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: smoking causes direct damage to the lungs, Fact2: Smoking causes irreversible lung damage by breaking the air sacs within the lungs., Question: What damages air sacs? (A) burning (B) coal (C) Oxygen delivered through cannulas (D) Smoking (E) Drinking alcohol (F) influenza (G) bacteria (H) Cardiovascular exercises
A:
D