Final answer:
Auditors typically use systems flowcharts to document their understanding of IT-based system controls for their ability to visually represent data flows and controls.
Step-by-step explanation:
Auditors document their understanding of IT-based system controls by using one of the following options: A. systems flowcharts, B. internal control questionnaires, or C. written narrative. To provide the correct option in the final answer, systems flowcharts are most often used by auditors to visualize and document the processes involved in IT-based system controls.
A systems flowchart details the flow of data, the steps in a process, and the controls in place, making it an effective way to understand and evaluate the control environment of an information system. In contrast, internal control questionnaires may be used to assess controls but are not as visual, while a written narrative can provide a thorough description but lacks the process flow visualization that a flowchart offers.