A control group is<em> a group of individuals in an experiment where the independent variable being tested (the exposition to cigarette smoke in this case) can't influence the results.</em> This control group will be then compared to the experimental group (exposed to the smoke) to see the effect of the variable evaluated.
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.B) You would place newborn curly-whiskered mud rats with bald mud rat parents and place newborn bald mud rats with curly-whiskered mud rat parents. Finally, let some mud rats of both species be raised by their own species. Then you would compare the outcomes.