C: Device twins change notifications allow back end applications to be notified in real-time of twin changes and react as business logic requires. For instance, when building an application that notifies an operator directly that a device has a firmware update pending and is "ready to update". This is accomplished by creating a routing rule from the "Twin Change Events" source and filtering all events that involve the software update status.
D: Applying enrichments
The messages can come from any data source supported by IoT Hub message routing, including the following examples:
* -->device twin change notifications -- changes in the device twin
* device telemetry, such as temperature or pressure
* device life-cycle events, such as when the device is created or deleted Reference:
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-message-enrichments-overview
https://azure.microsoft.com/en-us/blog/enhancements-to-azure-iot-hub-improve-management-of-the-full- device-lifecycle/