The correct answer is D. From the Finance site, configure permissions . Microsoft states that Microsoft 365 Copilot honors existing Microsoft 365 permissions and only grounds responses in content that the signed-in user is already allowed to access. That means if users are getting Finance-site content in Copilot responses, those users likely still have permission to that SharePoint content. The direct fix is to review and correct the site, library, folder, or file permissions on the Finance site so only the intended users retain access.
The other options do not directly solve this requirement. Information Barriers are designed for communication and collaboration segmentation scenarios, not for ordinary site-level oversharing remediation.
A Defender data connector is unrelated to SharePoint permission enforcement. Conditional Access controls sign-in and session access conditions, but it does not selectively remove Copilot grounding from one SharePoint site for users who still have site permissions. Because Copilot uses SharePoint and Microsoft Graph permissions as its boundary, the Microsoft-documented corrective action is to fix the Finance site permissions .