Final answer:
The correct answer to the student's question is C: prevention controls do not always have physical evidence indicating whether the control was performed. They can be procedural or based on soft controls and do not always leave tangible evidence, unlike detective controls which are meant to identify issues after they have occurred.
Step-by-step explanation:
The question asks which statement is true about prevention controls in the context of control systems within organizations or processes. Prevention controls are designed to deter or avoid undesired events or outcomes, and compared to detective controls, they're aimed at stopping problems before they occur. While they can have physical evidence to indicate whether the control was performed, it is not always the case. Thus, the correct answer is C. prevention controls do not always have physical evidence indicating whether the control was performed. This is because certain prevention controls may be procedural or based on soft controls like corporate culture or employee training, which don't always produce tangible evidence.
In contrast, detective controls are put in place to identify and alert organizations of issues post-occurrence, so they can take corrective action. The two, prevention and detective controls, are different concepts in internal control systems.
Experimental controls relate to the scientific method and typically refer to the procedures in a scientific experiment that minimizes the effects of variables other than the independent variable. This allows for a comparison between groups that differ only in one independent variable, enhancing the reliability of the results.