Final answer:
An administrator will be unable to delete a custom field when it is used in a page layout, used in a workflow field update, or part of a field dependency.
Step-by-step explanation:
An administrator will be unable to delete a custom field when it is:
- Used in a page layout
- Used in a workflow field update
- Part of a field dependency
When a custom field is used in a page layout, it is because it is necessary for capturing and displaying information on a specific page. If the field is deleted, it would break the layout and render the page unusable or incorrect.
In a workflow field update, the custom field is used to perform automatic updates based on certain conditions. Deleting the field would prevent the workflow from functioning as intended.
A field dependency is a relationship between two fields where the value of one field determines the values available in another field. If a custom field is part of a field dependency, deleting the field would disrupt this relationship.