Final answer:
A control group is crucial for controlling confounding variables, ensuring that differences in outcomes between the experimental group and control group can be attributed to the experimental treatment.
Step-by-step explanation:
A control group is vital in experimental design. It serves to minimize the effects of extraneous variables, ensuring that any observed differences in outcomes can be attributed to the experimental manipulation rather than to other factors. The control group does not receive the experimental manipulation and is used for comparison to determine the effect of the independent variable on the dependent variable.
Therefore, the correct answer to why a control group is used in an experiment would be to control for confounding variables.