Currently, there is an issue with the Automation Service. The configuration is not consistent over time. It fails to correct the configuration. Which of the following must be done to fix the issue?

Answer options:

A.Replace the Register-AzAutomationDscNode command with the Add-AzAutomationDscNode.
B.Change the value of the parameter “ConfigurationMode” for the Register-AzAutomationDscNode command.
C.Add the “AllowModuleOverwrite” parameter to the Register-AzAutomationDscNode command.
D.Add the “DefaultProfile” parameter to the Register-AzAutomationDscNode command.

Answer – B 
Here the main issue is that the “ConfigurationMode” parameter has been set to ApplyOnly, which means it will only apply the configuration once. 
Register-AzAutomationDscNode
-AzureVMName <String>
[-NodeConfigurationName <String>]
[-ConfigurationMode <String>]
[-ConfigurationModeFrequencyMins <Int32>]
[-RefreshFrequencyMins <Int32>]
[-RebootNodeIfNeeded <Boolean>]
[-ActionAfterReboot <String>]
[-AllowModuleOverwrite <Boolean>]
[-AzureVMResourceGroup <String>]
[-AzureVMLocation <String>]
[-ResourceGroupName] <String>
[-AutomationAccountName] <String>
[-DefaultProfile <IAzureContextContainer>]
[<CommonParameters>] 
-ConfigurationMode 
Specifies the DSC configuration mode. Valid values are: 

Since the issue is clear from the command, all other options are incorrect. 
For more information on Azure Automation, please visit the below URL- 

https://docs.microsoft.com/en-us/powershell/module/az.automation/register-azautomationdscnode?view=azps-5.0.0