Answer:
All of the above security policies could help detect fraudulent cases that occur even when other security controls are already in place.
Separation of duties helps by ensuring that no single person is solely responsible for the entire operation, thus reducing the risk of fraud.
Least privilege ensures that personnel are only allowed access to the information or resources they actually need to perform their roles, thus reducing the chances that information or resources can be misused.
Dual control is important because it ensures that at least two people are required to perform any sensitive or risky task, thus reducing the chance of any single person taking advantage of the situation to commit fraud.
Finally, mandatory vacations can help to detect fraudulent cases by providing an opportunity for other coworkers to review the work being done and possibly spot any suspicious activities that might otherwise have gone unnoticed.