You are operating an IoT solution of a large number of field devices. After several weeks of operation, you notice that a certain group of temperature sensors cease sending telemetry in the morning hours. You suspect that some kind of connection problems block messages and you decide to create a diagnostic setting in your IoT Hub, route the resource logs to Azure Monitor Logs and to analyze the log by running the following query: 
<pre class="brush:java;">AzureDiagnostics
| where ( ResourceType == "IOTHUBS" and 
Category == "DeviceTelemetry"
and Level == "Error")</pre>
Does it help you to localize the errors?

Answer options:

A.Yes
B.No

Correct Answer: B
Option A is incorrect because while sending logs to Azure Monitor Log is a right decision, the “DeviceTelemetry” category is used to track errors related to messages sent by the devices that are connected to the IoT hub. Therefore, “DeviceTelemetry” is not the right choice.
Option B is CORRECT because in order to find connection related error events in the log, the “Connections” diagnostic setting has to be configured (see below), and Category == “Connections” has to be used to filter the log entries.
Diagram: 

Reference: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-troubleshoot-connectivity#azure-monitor-use-logs-to-resolve-connectivity-errors