To test how fertilizer affects tomato plants, a farmer divided a field of young tomato plants into 10 plots of equal size. The farmer then put fertilizer on half of the plots and no fertilizer on the other half of the plots. What is the control group in this experiment?
A. All the weedy plants in all the plots
B. The tomato plants in all the unfertilized plots
C. The tomato plants in all the fertilized plots
D. All the tomato plants in the field