Question ID:PT78 S1 Q5 Passage:Researchers asked 100 fifty-year-olds and 100 twenty-year-olds whether they gave blood. Because nearly twice as many fifty-year-olds as twenty-year-olds reported that they sometimes gave blood, the researchers concluded that, on average, fifty-year-olds are more altruistic than twenty-year-olds. But there is reason for skepticism. Many people hesitate to admit that their behavior does not conform to societal expectations. Stem:The reasoning above calls into question a conclusion drawn from statistical data by Correct Answer Choice:BChoice A:showing that the data are based on an unrepresentative sample Choice B:offering an alternative explanation of some of the data Choice C:showing that one cannot directly observe altruism Choice D:criticizing the motives of the researchers Choice E:offering a specific counterexample