IoT Hub generates messages on occurrence of certain events. Relying on this feature you want to send email alerts to the operations when critical devices become unavailable. You want to use Azure Event Grid with Logic Apps. Here are the steps you should consider while building the required solution: Create an event subscription in IoT Hub (Device Disconnected)
Create an Event Grid connection
Define Logic App trigger event (Microsoft.Devices.DeviceDisconnected)
Devine a Webhook endpoint in IoT Hub for Logic App function
Define an Azure Functions endpoint in IoT Hub
Configure Logic App action (send email)
Define a message route to Event Grid in IoT Hub 
Which steps should be executed in what order?

Answer options:

A.2, 6, 1, 4
B.3, 6, 1, 7
C.3, 6, 1, 4
D.3, 6, 1, 5

Correct Answer: C
Option A is incorrect because you don’t set up an Event Grid connection explicitly. In this case, it is created implicitly by configuring an event in Logic App.
Option B is incorrect because, on one hand, Event Grid is not a custom endpoint and you cannot configure it as a routing target. On the other hand, Event Grid actions must be configured as Events in the IoT Hub, instead of message routes.
Option C is CORRECT because first you need to define a Logic App trigger event using the DeviceDisconnected schema; then the action invoked by the trigger must be set; then you need a publish topic in IoT Hub and an event subscription; finally the endpoint type must be set to Webhook.
Option D is incorrect because you need to use the Web Hook (not Azure Functions ) as event handler for Logic Apps to implement a logic to process Event Grid events.
Reference: 

https://docs.microsoft.com/en-us/azure/event-grid/publish-iot-hub-events-to-logic-apps