What should you use to detect which documents are sensitive?

You have a Microsoft 365 subscription that uses Microsoft Defender for Office 365.
You have Microsoft SharePoint Online sites that contain sensitive documents. The documents contain customer account numbers that each consists of 32 alphanumeric characters.
You need to create a data loss prevention (DLP) policy to protect the sensitive documents.
What should you use to detect which documents are sensitive?
A. SharePoint search
B. a hunting query in Microsoft 365 Defender
C. Azure Information Protection
D. RegEx pattern matching