Passage Summary: Even though some cigarettes are marketed as having less nicotine, people who smoke a pack a day end up with the same amount of nicotine in their systems no matter which type they smoke.

Reasoning: A study found that smokers who consume one pack a day have identical nicotine levels in their blood regardless of whether their cigarettes are low-nicotine or high-nicotine.

Analysis: The paradox here is the discrepancy between the product's content and the smoker's biological levels. If the cigarettes have less nicotine, why isn't there less nicotine in the blood? We need an explanation that accounts for how the smokers are getting that extra nicotine. Look for an answer that suggests a change in human behavior, such as low-nicotine smokers inhaling more deeply or smoking more of the cigarette to compensate for the lower concentration.