Question

HELP ME ASAP PLS :)

Answer 1

Answer:

A or D

Step-by-step explanation:

I would think that it would be a valid sample because the first nine people were selected to participate.  But, it also could not be a valid sample because it is only a short study.  If there are more than one answer, I would say those two, but if it is only one answer, it is either A or D.  I think....