You are operating the IoT infrastructure of a company manufacturing chemical compounds in five geographical locations. In the previous years, all the sites were equipped with a number of field sensors which are now registered to Azure IoT hubs, via the automatic provisioning service. One of the lines of businesses being sold, devices at site B must be decommissioned from the system and they must be prevented from provisioning again in the future. 
Which two of the following steps should you execute to meet the requirement?

Answer options:

A.Disable the X.509 certificate in Device Provisioning Service
B.Delete the device identities from IoT Hub
C.Delete the enrollment group from DPS
D.Disable the enrollment group in DPS
E.Disable the devices on the IoT Hub

Correct Answers: B and C
Option A is incorrect because you cannot disable the X.509 certificate in DPS. What you can do is disable the enrollment group (which invalidates the certificate, implicitly).
Option B is CORRECT because of the change of ownership, you need to permanently remove the devices from the IoT hub’s registry, in order to prevent future communications and data transfer. Therefore, you need to delete the device`s entry from the identity registry.
Option C is CORRECT because, in order to prevent devices from automatically re-enrolling to DPS, their entrymust be permanently removed from the provisioning service.
Option D is incorrect because, for the given scenario, you have to ensure that the devices will not be able to re-provision after being decommissioned. The enrollment entries must be deleted instead of getting disabled.
Option E is incorrect because, for the given scenario, you have to ensure that the devices will not be present in the IoT hub any more, after being decommissioned. The identities entries must be deleted from IoT hub.
Reference: 

https://docs.microsoft.com/en-us/azure/iot-dps/how-to-unprovision-devices