Select the correct answer. A group of researchers carried out a study to determine which type of portable water purification system is the most effective. Throughout the study, they used water from a variety of lakes in the region.

Which conclusion could be reported based on this study?

A.
The portable water purification system that is found to be the most effective will work for all bodies of water.
B.
The portable water purification system that is found to be the most effective will work only for lake water.
C.
The study will produce results regarding the effect of the portable water purification systems only on lake water in that region.
D.
The study is inherently biased, and no results can be reported.