You are operating an industrial IoT infrastructure solution of a chemical plant with sensors to monitor possible NH3 contamination in the air. The telemetry data from the sensors are sent to an IoT Hub. You have to build a device monitoring solution that triggers alerts immediately when any of the sensors lose connection. You want to solve the problem by Azure services like Azure Monitor or Event Grid. 
Which one of the two services are you recommended to choose and why?

Answer options:

A.Choose Event Grid because of its easier integration with IoT Hub
B.Choose Azure Monitor because of its ability to track individual devices
C.Choose Azure Monitor because it has predefined DeviceConnected/Disconnected events for the devices to subscribe to
D.Choose Event Grid because its ability to track individual devices

Correct Answer: D
Option A is incorrect because using Event Grid requires integration with other Azure services (e.g. Function App) to deliver notifications. While Azure Monitor is easier to set up, it doesn’t provide the required low latency and device-level tracking.
Option B is incorrect because Azure Monitor is capable of tracking individual devices. With Azure Monitor, you can use a metric, Connected devices, to monitor the number of devices connected.
Option C is incorrect because it is the Event Grid which has the DeviceConnected and DeviceDisconnected events to which the critical devices can subscribe to. There is no such feature in Azure Monitor.
Option D is CORRECT because Event Grid is capable of tracking connect and disconnect events for individual devices and to use it to send per-device notifications, with low response time. This is the recommended choice for production environments.
References: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-troubleshoot-connectivity#event-grid-vs-azure-monitor
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-event-grid#event-types