Answer: C.article documenting experiments with their results
Explanation:
An independent variable is the variable that can be changed or manipulated so as to determine the result of such change on the dependent or the experimental variable.
In the given study, the color of light is the independent variable the effect of which is to be determined over the plant growth which is the dependent variable.
The information related to this experiment can be observed on the article documenting the experiments similar experiment. This will have valid and reliable information.
