Answer: D. Performing a fair test in which only the independent variable affects the dependent variable.
Explanation:
Validity is a measure of how correct the result of the experiment is. The validity of the experiment is based upon the correctness of the research topic, and correctness and implementation of the scientific procedures.
Performing a fair test that can be based upon use of the independent and dependent variables can yield results which will be valid and acceptable. The independent variable in an experiment is the variable which can be changed to know it's affect on the dependent variable. The dependent variable will help in determining the result of the experiment.
