Final answer:
In the given scenario, the rats administered 100 ng/g BPA would belong to the treatment group.
Step-by-step explanation:
In the given scenario, the rats administered 100 ng/g BPA would belong to the treatment group. In any experiment, the control group is the group that does not receive the experimental treatment, while the treatment group is the group that does receive the experimental treatment. Since the rats in this case are being administered BPA, they are receiving the experimental treatment and hence belong to the treatment group.