An experiment was designed to test the effect of ultraviolet light on the growth of mold spores. A sample of mold spores was divided into two groups. The groups were grown under the same conditions, except that group A was exposed only to ultraviolet light and group B was grown in total darkness. What is the purpose of group B being grown in total darkness?

To limit bias

It is the dependent variable

It is the control group

To add an alternative variable