To 'undo' a mistaken import, the administrator must delete the incorrectly created records. Two standard tools facilitate this:

Mass Delete Records (Option D): This is a browser-based tool in Setup that allows administrators to delete up to 250 records at a time (standard) or use criteria to identify and remove larger sets of records. It is the quickest way for smaller mistakes.

Data Loader (Option B): For large-scale errors, the administrator can use the Success file generated during the original import (which contains the new record IDs) and perform a 'Delete' operation.

The Data Import Wizard (Option C) is for adding or updating data, but it does not have a 'Delete' function. Weekly Data Export (Option A) is a backup tool and cannot be used to remove existing data from the system.