What must be done to confirm a password during document encryption in PowerPoint?

To confirm a password during document encryption in PowerPoint, the process requires the user to type the password again in the Confirm Password dialog. This step is crucial because it ensures that the user has correctly entered the password without any errors, such as typos or misspellings. By requiring the user to re-enter the password, PowerPoint helps to safeguard against mistakenly setting a password that could be forgotten or lead to access issues later on.

The other options do not provide the necessary steps for confirming the password. While answering a security question adds another layer of protection, it is not part of the password confirmation process. Clicking 'Save' in the document settings is important for saving changes but does not address the password confirmation directly. Similarly, entering a new password in the main dialog is part of the initial password setting and not the confirmation process itself. Thus, re-entering the password in the Confirm Password dialog is the essential action required for proper password validation in document encryption.