Deleting an object in such a system is inconvenient because all changes must be made to the control lists of all subjects who did have access to the object. Suggest an alternative, less costly means of handling deletion

Answer explained below

Explanation:

Suppose a per subject access control list is used. Deleting an object in such a system is complex process because all changes should be made to control lists of all subjects who did have access to the object. An alternative, less costly means of handling deletion is placeholder which can be used to delete the content of different subject lists.

The content of different subject lists can also be erased if the access codes of the original user in the server of the per-subject are changed