This configuration correctly implements the principle of least privilege. Site admins in the Owners group get Full Control to manage the site. Senior auditors in the Members group get the default Contribute permission level, allowing them to add, edit, and delete items. For junior auditors, a custom permission level (e.g., a copy of Contribute with "Delete Items" and "Edit Items" permissions removed) assigned to a new group is necessary to meet the specific requirement of only allowing file uploads.

A. The Visitors group has Read-only permissions by default, which would prevent junior auditors from uploading files as required.

C. Placing all users in the Owners group grants excessive permissions to auditors, violating fundamental security best practices.

D. This option assigns insufficient permissions to site admins (Members) and junior auditors (Visitors cannot upload files).

1. Microsoft Learn. (2023). Default SharePoint groups. This document defines the default permissions for Owners (Full Control), Members (Contribute), and Visitors (Read).

2. Microsoft Learn. (2024). How to create and edit permission levels. This guide details the process for creating custom permission levels, which is required to meet the junior auditor requirement. It states, "You can create a new permission level... by copying an existing permission level and changing it."

3. Microsoft Learn. (2023). Understanding permission levels in SharePoint. The table "Default permission levels" shows that Contribute includes "Add, edit, and delete list items," confirming a custom level is needed to restrict junior auditors.