You will be given a definition of a task first, then some input of the task.
In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to prevent emphysema [title] Stop smoking. [step] Tobacco smoke is a recognized cause of emphysema and other forms of chronic obstructive pulmonary disease (copd), such as chronic bronchitis and asthma. The best way to avoid emphysema is to never start smoking. <sep> (A) If you're currently a smoker, quitting can help improve your health, even after years of smoking. [substeps] Smoking is the cause of emphysema in 80% to 90% of all reported cases. (B) This will only reduce your overall risk of emphysema by increasing your level of heart health. [substeps] As a general rule, do not smoke more than six hours each day. (C) Smoking gets all over your body and impairs your ability to see, smell, and feel the world. In particular, do not smoke just before bedtime. (D) If your schedule permits, stop smoking, no matter how far behind your limit or how many hours a night you have. If you're taking other medications, consult with your doctor before starting a new course of treatment.
Output:
A