Final answer:
The correct solution to ensure an Actual Salary value is entered when an offer is accepted in a recruiting application is to create a validation rule that prevents saving the offer record if the Actual Salary is null at the time of acceptance.
Step-by-step explanation:
The requirement is that once an offer has been accepted by a candidate, the Actual salary field must contain a value. The correct way to implement this requirement in a recruiting application is to create a validation rule that checks whether the Actual Salary field is not null when the status of an offer indicates that it has been accepted. This can be achieved by setting up a validation rule with criteria like IF(AND(Status__c = 'Accepted', ISBLANK(Actual_Salary__c)), true, false), which will ensure that the offer record cannot be saved unless the Actual Salary field is filled out when the offer is accepted.