The correct answer is demanding. This is not a form of sanitation. Overwriting, degaussing, and destruction are all methods of sanitation.

Purging media: removes all data by writing over existing data multiple times to ensure that the data is not recoverable using any known methods. Purged media can then be reused in less secure environments.

Clearing, or overwriting: writes unclassified data over existing data, but some sophisticated forensics techniques may be able to recover the original data, so this method should not be used to reduce the classification of media. Sophisticate tools can recover, but normal tools/function may not be able to reconstruct the data.

Erasing: the media performs a delete, but the data remains and can easily be restored.