The correct answer is D. Dependent variable.
Explanation
When an experiment is being carried out, it is necessary to clarify that there must be two variables, one of them is independent and the other is a dependent variable. The first, as its name implies, is a fixed variable, which does not depend on any condition of the experiment and cannot be changed or modified. On the other hand, the dependent variable is one that changes from different factors, such as temperature, chemical compounds, elements, among others that are independent variables. Therefore, the correct answer is D. Dependent variable.