Final answer:
A software application restricting sales over a customer's credit limit is an example of a preventive control, designed to stop undesired events before they happen.
Step-by-step explanation:
A software application that does not allow a sale to be processed if a customer is over its credit limit is an example of a preventive control. This type of control is designed to prevent an undesirable event from occurring, in this case, extending credit beyond a customer's limit. It is not a detective control, which would identify an issue after it has occurred, nor an IT-dependent manual control, which involves human intervention. Lastly, it is not an IT general control, which focuses on the overall IT environment rather than specific transaction-level concerns.