Setting the value of a field according to workflow rules is contingent on specific record states and actions. The correct answer highlights a situation where workflow rules cannot alter field values, which occurs when editing an existing record.
When editing an existing record, the values in fields may already depend on existing data or other rules in effect. However, workflow rules typically have specific conditions and events under which they trigger to modify field values. For workflows to modify values, they rely on pre-defined triggers, which might be limited when a record is already in an editable state.
In contrast, during the creation of a new record, workflow rules can be set to initialize values as the record is being constructed. Similarly, when deleting a record, workflow actions do not apply, as the record itself is being removed rather than updated. Lastly, prior to a record being viewed, the workflow can still apply modifications to field values since the record is not yet finalized in the user's context.
Understanding when workflow rules can or cannot apply changes to fields is essential for effectively managing data integrity and ensuring that updates occur only under the correct circumstances.