You have some smart thermostat devices deployed that need to receive prescribed temperature values as well as, in some cases, restart commands from the IoT Hub. The communication is only allowed over port 443, and latency of the delivery is not critical. 
Which protocol is not suitable for the given scenario?

Answer options:

A.MQTT over Websockets
B.AMQP over Websockets
C.HTTPS
D.MQTT

Correct Answer: D
Option A is incorrect because MQTT over Websockets communication goes over port 443 and it is a great choice for bi-directional communication, even in latency-critical scenarios.
Option B is incorrect because AMQP over Websockets communication goes over port 443 and it is a great choice for bi-directional communication, even in latency-critical scenarios.
Option C is incorrect because HTTPS communication builds on port 443. It can be used to push cloud-to-device messages but it is recommended to use in non-latency-critical scenarios.
Option D is CORRECT because MQTT communicates on port 8883.
References: 

https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-devguide-protocols
https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-protocol-gateway