How many blacks fought to free the slaves? a.
45,000
c.
145,000
b.
85,000
d.
185,000

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?