The correct answer is Linux Diagnostic Extension (LAD) 3.0.

Linux Diagnostic Extension (LAD) 3.0 is the VM extension designed to collect performance metrics and diagnostic logs from Linux virtual machines. It can gather metrics, syslog entries, and performance counters and deliver those diagnostics to configured storage or monitoring endpoints when it is installed on the VM.

Note that Microsoft is moving to a newer unified agent and tooling. The legacy extension may still be the expected answer for scenarios that specifically name the extension, but customers are being encouraged to migrate to modern agents for long term use.

Azure Monitor agent is incorrect for this question because it is the newer unified agent that Microsoft recommends for collecting telemetry across resources. The exam scenario specifically expects the Linux diagnostic extension and older course material and labs often reference LAD instead of the newer agent.

Azure Performance Diagnostics extension is incorrect because it is not the standard VM extension used to collect general performance metrics and diagnostic logs from Linux virtual machines. It is not the agent that configures continuous metric and log collection in the way that the diagnostics extension does.

Azure HDInsight is incorrect because it is a managed big data service and not an extension or agent for collecting VM performance metrics or diagnostic logs.

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