You are building an industrial IoT solution for a manufacturing plant equipped with a number of field devices which communicate using the Modbus protocol. Because of security and traffic monitoring reasons, you want the devices to connect to the IoT Hub via an edge device. 
How would you configure the solution for this scenario?

Answer options:

A.No IoT Hub identity is needed for the leaf devices; Use edge as a translation gateway
B.Create IoT Hub identity for each leaf device; Use edge as a transparent gateway
C.No IoT Hub identity is neededfor the leaf devices; Use edge as a transparent gateway
D.Create IoT Hub identities for the leaf devices; Use edge as a translation gateway

Correct Answer: A
Option A is CORRECT because so that the field devices can communicate with the IoT Hub, their protocols need to be translated. This translation role can be played by a protocol translation gateway. In this case, the devices don’t have IoT Hub identities.
Option B is incorrect because the Modbus devices cannot communicate with the IoT Hub directly. Protocol translation is needed and the devices must be connected to the IoT Hub through the edge gateway device. Therefore, transparent gateways are not suitable for the given scenario.
Option C is incorrect because the Modbus devices cannot communicate with the IoT Hub directly. Protocol translation is needed and the devices must be connected to the IoT Hub through the edge gateway device. Therefore, transparent gateways are not suitable for the given scenario.
Option D is incorrect because while the translation gateway is the right solution here, there will be no IoT Hub identities created.
Diagram: 

Reference: 

https://docs.microsoft.com/en-us/azure/iot-edge/iot-edge-as-gateway?view=iotedge-2018-06#protocol-translation