take care to do中等

Though all the subjects were drawn from a population of European extraction, care was taken to [see] that all subjects, friends and strangers, were taken from the same population.

尽管所有受试者都来自欧洲血统的人群，但研究人员仍注意确保所有受试者——无论朋友还是陌生人——都取自同一人群。