You should be prepared with all of the following prior to looking at properties EXCEPT: A. current and previous addresses B. employer and length of employment C. personal references D. no advance preparation

Chen's research team randomly assigned some newborns and their mothers either to a breastfeeding promotion group (where breastfeeding was encouraged, but not required) or to a normal pediatric care group (where breastfeeding was neither encouraged nor discouraged). which research method did they use?