You have just created a device identity in your IoT Hub named mytemphub-001. You want to enable your back-end application to connect to this IoT hub and to access the messages. You need a connection string which you retrieve by the following CLI command: 
<pre class="brush:java;">az iot hub connection-string show \
--policy-name service \
--name {YourIoTHubName} \
--output table
</pre>
Is that the command you should use?

Answer options:

A.Yes
B.No

Correct Answer: A
Option A is CORRECT because to enable back-end applications to connect to your IoT hub you need the service connection string which can be retrieved by the command above.
Option B is incorrect because the command above is actually for retrieving the service connection string needed by the back-end applications. Field devices would need adevice connection string:
<pre class="brush:java;">az iot hub device-identity connection-string show --hub-name {YourIoTHubName} --device-id MyPythonDevice --output table
</pre>
Reference: 

https://docs.microsoft.com/en-us/azure/iot-hub/quickstart-control-device-python#register-a-device