Final answer:
An auditor would likely examine documentation of control activities to verify whether internal control activities are operating as designed, as it provides direct and reliable evidence.
Step-by-step explanation:
To determine whether internal control activities are operating as designed, an auditor would most likely examine documentation of control activities. This includes reviewing policies and procedures, examining records, and ensuring that the controls are being applied consistently. Documentation provides evidence that control activities have been established and are being maintained. This evidence is more direct and reliable than other options such as analytical procedures, confirmation letters, or inquiry of management, which are less direct and may not provide the same level of assurance as to the operation of the controls.