The Security Reader role is the most appropriate choice as it adheres to the principle of least privilege. This role grants read-only access to security-related information, including viewing alerts and reports within the Microsoft Purview compliance portal and the Microsoft 365 Defender portal. Assigning this role allows the user to view Data Loss Prevention (DLP) alerts without granting them unnecessary permissions to manage or modify policies, data, or security configurations.

A. Compliance Administrator: This role has extensive permissions to manage all compliance features, which violates the principle of least privilege as the user only needs to view alerts.
C. Security Operator: This role can manage and remediate alerts, granting more permissions than the required read-only access.
D. Compliance Data Administrator: This role is focused on managing data within compliance solutions like eDiscovery, not primarily on viewing security alerts.

1. Microsoft Learn. (2024). Permissions in the Microsoft Purview compliance portal. "The Security Reader role group... Members can review security-related information and reports in Microsoft 365 Defender portal and Microsoft Purview compliance portal. This includes reading reports, and viewing alerts and incidents." https://learn.microsoft.com/en-us/purview/microsoft-365-compliance-center-permissions#roles-in-the-microsoft-purview-compliance-portal-and-microsoft-365-defender-portal

2. Microsoft Learn. (2024). Learn about alerts in Microsoft Purview Data Loss Prevention. "To view DLP alerts, you need to be assigned to the... Security Reader... role group." https://learn.microsoft.com/en-us/purview/dlp-learn-about-alerts#permissions