The dominate climate region in Southeast Asia is . A. tropical wet B. highlands C. tropical wet and dry D. humid subtropical Please select the best answer from the choices provided A B C D

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?