Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Emphysema is a lung disease in which walls of the alveoli break down so less gas can be exchanged in the lungs (see Figure below ). This causes shortness of breath. The damage to the alveoli is usually caused by smoking and is irreversible. Answer: lungs
A:
What part of the body does emphysema affect?