Final answer:
The correct answer is 4) Aids in the professional development of the operating staff.
Step-by-step explanation:
Engagement working papers are used in the field of accounting and auditing. They provide documentation of the planning, performance, and review of engagements, thereby aiding in the quality control of the work performed.
Engagement working papers also serve as the principal support for engagement communications, as they contain important information about the work done and the conclusions reached. They can be used to facilitate third-party reviews by providing necessary information and evidence.
However, engagement working papers are not specifically intended to aid in the professional development of the operating staff. While they can provide insights and learning opportunities for staff members, their primary purpose is to ensure the proper execution and documentation of engagements.