You have smart devices deployed around your IoT landscape. You need to monitor their operation health. You experience that some of the devices have connectivity issues from time to time. 
Which part of the module twins should you explore first to troubleshoot the problem?

Answer options:

A.$EdgeHub.properties.reported
B.$EdgeAgent metadata
C.$EdgeAgent.tags and .properties
D.$SecurityDaemon.properties.reported

Correct Answer: B
Option A is incorrect because the $EdgeHub module twin contains data about communications between the IoT Edge hub running on a device and your Azure IoT hub. For connectivity issues in general, you should start investigating the $EdgeAgent first.
Option B is CORRECT because it is the EdgeAgent that is responsible for monitoring the operation of modules on your device. $EdgeAgent contains connectivity and health data of the modules deployed. In case of connectivity issues, you should start here, with examining the status and last update time, before digging deeper.
Option C is incorrect because while troubleshooting, you should look for information coming from the device. The .tags section of the device/module twins is only visible for the backend services; you’ll find no live data reported by the device there.
Option D is incorrect because the IoT Edge security daemon is responsible for the operations of IoT Edge security manager. It represents a portion of the computing base of the IoT Edge device. For connectivity-related information, look at the $EdgeAgent first.
References: 

https://docs.microsoft.com/en-us/azure/iot-edge/how-to-monitor-module-twins?view=iotedge-2018-06#monitor-iot-edge-agent-module-twin
https://docs.microsoft.com/en-us/azure/iot-edge/how-to-monitor-iot-edge-deployments?view=iotedge-2018-06