Answer :
This question is incomplete because the options are missing; here are the options:
Which statement describes what Levi did to prepare the control group in his experiment?
A) Levi held all experimental factors constant except for fertilizer.
B) Levi did not apply any fertilizer to one of his plants.
C) Levi applied different amounts of fertilizer to three of his plants.
D) Levi measured his plants on five separate days.
The answer to this question is B. Levi did not apply any fertilizer to one of his plants.
Explanation:
In an experiment, the control group refers to the subject or subjects, in this case, the plants, that do not receive the treatment or variable tested by the researcher. This implies the control group for Levi is the plant with no fertilizer because this is the only plant that does not receive the treatment or fertilizer. Moreover, this acts as a control group because Levi can use this plant to determine if the growth of the other three plants is positively or negatively affected by the use of the fertilizer.