Demarcus drinks several cups of coffee a day. often, demarcus experiences an almost immediate sense of alertness when he smells a fresh cup of coffee, even though it takes about 20 minutes for the caffeine in the coffee to reach significant levels in the bloodstream. he decides, with the encouragement of his physician, to quit drinking coffee. at first, he still experiences the alertness when he smells freshly brewed coffee, but after about 10 days, he no longer experiences the effect. that demarcus no longer experiences the alertness effect exemplifies: