Jane and Jill wondered if plant shoots always grew up toward the light. The two girls planted several pots of seeds . After the seeds germinated, they removed them from the soil and and repositioned the seeds in the ground. They place one-third in the normal position for growth, roots down and shoots up . This was the control group. They placed another third up-side down or shoots down and roots up. They placed the last group on their sides so the shoots and roots were both oriented horizontally. What else should the girls do in order to ensure that their results are valid? A Fertilize the two experimental groups but not the control group. B Place one group of seeds outside and keep the other two groups indoors. C C Be sure all other conditions remain constant throughout all three groups. D D Keep the control group in the pot but place the other two groups in the soll.