Task: Explanation
Input (English): Question: Suppose that Mary hasn't started smoking yet. If you measured the oxygen levels in her blood now and compared them to oxygen levels after she's been smoking for 20 years, what would you find? 
 Answer: more oxygen in her blood now
Output (English): Smoking reduces the amount of oxygen available for diffusion at the lungs, so less oxygen gets absorbed and blood is oxygenated to a lesser degree.