C. Experimental
Explanation - The cause and effect of a process would be studied in experimental investigations. However, in descriptive studies, relationship between the factors are not studies rather the detail of the process is studied. In comparative investigation, several factors are compared and its effects are analyzed.
In experimental investigations, experiments are carried out based on the hypothesis and then it is validated accordingly. Validation is a must to prove and disprove the hypothesis. Therefore, experimental data and hypothesis are related.
