Final answer:
A hash total is an example of an application control which auditors review to ensure transaction processing accuracy within IT systems.
Step-by-step explanation:
Regarding a client's IT controls, auditors must differentiate between general controls and application controls. Among the options provided, hash total is an example of an application control. Application controls are focused on the validity, completeness, and accuracy of the transactions during the processing stages. For instance, hash totals involve summing up a numerical value (which is not necessarily a valid financial total) for a batch of transactions to ensure that the batch is processed correctly from start to end, without missing or duplicate transactions.