Most nicotine is absorbed into the blood of a smoker even if it is delivered in smaller quantities. Smokers of the lowest-nicotine cigarettes available generally smoke more cigarettes per day than smokers of high-nicotine cigarettes. The level of tar in cigarettes is higher in low-nicotine cigarettes than it is in some high-nicotine cigarettes. Blood cannot absorb more nicotine per day than that found in the smoke from a package of the lowest-nicotine cigarettes available.
Cigarette companies claim that manufacturing both low-and high-nicotine cigarettes allows smokers to choose how much nicotine they want. However, a recent study has shown that the levels of nicotine found in the blood of smokers who smoke one pack of cigarettes per day are identical at the end of a day' s worth of smoking, whatever the level of nicotine in the cigarettes they smoke.
Which one of the following, if true, most helps to explain the finding of the nicotine study?