Researchers identified situations that would evoke either no, mild levels, or moderate levels of stress. they brought 60 people individually into a lab and presented three conditions sequentially, counting how many of the snacks were eaten during each episode. the order of presentation was varied across participants. one-third of the people did no-mild-moderate stress; another third did mild-moderate-no stress, and the final third did moderate-no-mild stress. this is a study a. matched pair b. 2x2 design with one within and one between variable c. within s's d. between s's