Katrina and Carla are twin sisters of the fraternal type. They have different groups of friends, different interests, and different personalities. Katrina is described as antagonistic, offensive, and unfriendly, whereas Carla is described as warm and easygoing. These twins differ on the factor of the five-factor model.

According to the federal regulations, which of the following studies meets the definition of research with human subjects? a. a researcher uses the customs office’s passenger lists for ships bringing immigrants to the us between 1820-1845 to track the numbers of immigrants from certain ethnic groups. b. a researcher conducts a linguistic study of comments posted on a local public blog. c. a developmental psychologist videotapes interactions between groups of toddlers and their care givers to determine which intervention methods most effectively manage aggression. d. a researcher asks the director of a local free clinic about the number of patients in the last two years with newly diagnosed hiv/aids.