Scientific Investigation of the Exact Effects of Environmental Steroids on Humans

Scientific investigation of the exact effects of environmental steroids on humans is extremely difficult since there are multiple sources of hormones in the environment. A valid study would require a control group that has not been exposed to the chemicals being studied. Since everyone has had some exposure to environmental hormones, no control group is available to use as a reference.
Another way to assess the environmental hazard due to steroid hormones is to analyze the amount of residual hormones present following commercial water treatment by water treatment plants.
-Which situation would make researchers suspect that there was an excess of steroid hormones in the environment?

A) an increase in foot fungal infections
B) an increase in mutation rate in amphibians in the area
C) premature puberty in girls in the area
D) an increase in bone fractures in seniors in the area