Respuesta :
C.Divide them into groups based on similarities would be my answer
Answer:
D. Divide them into groups randomly
Step-by-step explanation:
The point of blocking is to ensure randomization. To have an unbiased experiment, you need randomization, because if your groups are unbalanced (say, we have one group all females and one group all males) you can't attribute your findings to the variable under study, because of the possibility that it could be due to other noise factors.