You need to recommend a solution that will monitor Azure subscription activity and send alerts to a non-Azure system for processing.
Notification of alerts sent to the external system must be automated.
Which mechanism should you recommend?
You should recommend using a webhook. Azure alerts use HTTP POST to send the alert contents in JSON format to a webhook URI that you provide when you create the alert. Azure posts one entry per request when an alert is activated.
You should not recommend Power BI. This service is used to present and analyze both historical and live data. The external system would need to retrieve the data from Power BI.
You should not recommend Azure Event Hubs. Although this service is used to ingest data, you would need an additional component to send data to an external system.
You should not recommend Azure Stream Analytics. This service is used to process large amounts of data on the fly and to perform complex data analytics and aggregations.