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 Y and a control group with no fertilizer.

B.two groups of plants—a group fertilized by X 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.