Answer:
The experimental variable is the expossure to antibacterial kitchen spray and the control variables are the nutrient agar, the cotton swab and the conditions of incubation as well as the period of incubation.
Step-by-step explanation:
As you can see in the introduction for your practice, an experimental variable, is a variable that you manipulate in an experiment. In this case Julie add antibacterial kitchen spray only to one of the Petri dishes, not to both.
Control variables are the ones that remains the saame during the assay. In this case, nutrient agar, cotton swab and conditions and time of incubation did not change.