A scientist wants to determine which fertilizer is more effective—Fertilizer X or Fertilizer Y. The best way for her to proceed would be to design an experiment with A. two groups of plants—a group fertilized by X and a control group with no fertilizer. B. two groups of plants—a group fertilized by Y and a control group with no fertilizer. C. three groups of plants—a group fertilized by X, a group fertilized by both X and Y, and a control group with no fertilizer. D. three groups of plants—a group fertilized by X, a group fertilized by Y, and a control group with no fertilizer.