A farmer grows and sells flowering plants. The best-selling plants are the ones with the most blossoms. The farmer reads an advertisement for a plant food saying that it will make plants grow faster and taller. The farmer predicts that taller plants will have more blossoms and performs the following experiment to test this hypothesis. Two groups of 10 plants each are grown in identical pots filled with equal amounts of identical soil. The amount of sunlight, the room temperature, and the amount of water are held constant for both groups. Group A is given plant food at regular intervals according to the instructions on the package. Group B is not given plant food. The farmer observes the plants after 15 weeks of growth. The results are recorded below. Why are the amount of sunlight, the room temperature, and the amount of water held constant for both groups? A To ensure only the independent variable is being tested B To ensure only the dependent variable is being tested C To reduce costs of the experiment D To make sure flowers bloom