TOPIC: question on scope creep

Hello. I have a doubt on the following question that I came across in one of the exams -

Scope creep - many answer results, including the ones at PM Simulator state that scope creep can be prevented by control scope - however, one answer that was given in one of the exams administered by another site was Work Authorization System (WAS) rather than scope statement or control scope - is this is the correct answer? The explanation stated that WAS is a key tool to prevent scope creep - this is the first time that I heard about this as a tool to combat scope creep.

If you can help me understand the above better, that would be most helpful. Thanks.

WAS allows tracking and authoring the work to be done at the right time in a proper sequence. This system would help to avoid scope creep as the team member would not be able to add anything 'extra' without appropriate authorization.

Control scope ensures - requested changes, recommended corrective/preventive actions are performed through PICC process. Control scope also manages the actual changes as they occur (by integrating them with other processes) .... However WAS will prevent them to occur .