Answer: light
Explanation:
In experiments variables are required to be chosen so as to prove a theory. An independent variable is the one which be changed manually. The effect of such change can be observed on the dependent variable. The dependent variable is the outcome of the experiment.
In the given situation, the plant growth is monitored on the basis of availability of light. It was kept in darkness as well as in artificial light to know the fact that how light contributes to plant growth.
Therefore, plant growth is dependent variable. The plant receiving light or not is the independent variable.
