Which of the following types of data are free to ingest to Azure Sentinel? (choose all that apply)

Answer options:

A.Azure Diagnostics Logs
B.Microsoft 365 Defender Alerts
C.Azure Activity Logs
D.Logs ingested into Custom Tables

Correct Answers: B and C 
The following data sources are free with Azure Sentinel: Azure Activity Logs.
Office 365 Audit Logs, including all SharePoint activity, Exchange admin activity, and Teams.
Microsoft Defender alerts, including alerts from Azure Defender, Microsoft 365 Defender, Microsoft Defender for Office 365, Microsoft Defender for Identity, and Microsoft Defender for Endpoint.
Azure Security Center and Microsoft Cloud App Security (MCAS) alerts. However, raw logs for some Microsoft 365 Defender, MCAS, Azure Active Directory (Azure AD), and Azure Information Protection (AIP) data types are paid.
Reference: 

https://docs.microsoft.com/en-us/azure/sentinel/azure-sentinel-billing