HOTSPOT
You are the Microsoft Exchange Online administrator for your company. The company has
been using Exchange Online for over two years.
Employees report that items are disappearing from their primary mailboxes. You discover
that an old retention policy is enabled for the employee mailboxes.
You need to ensure that items are not automatically removed from employees’ primary mailboxes.
How should you complete the relevant Windows PowerShell script? To answer, select the
correct code segment from each list in the answer area.
Answer: 
Explanation:
The example is using the -Filter parameter of Get-Mailbox and filtering on the “ReceipientTypeDetails” property of which only the “UserMailbox” is a valid option. See this article:
https://technet.microsoft.com/en-us/library/bb738155(v=exchg.150).aspx
Removing the retention policy must be done by setting it to $null:
https://technet.microsoft.com/en-us/library/bb123981%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396
http://o365info.com/manage-retention-policy-by-using/
Looks good to me.
https://technet.microsoft.com/en-us/library/bb738155(v=exchg.150).aspx
https://technet.microsoft.com/en-us/library/bb123981%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396
http://o365info.com/manage-retention-policy-by-using/
I feel this one is correct. You must clear the retention policy by setting it to $null and filtering on RecipientTypeDetails -eq ‘UserMailbox’ is also correct.
https://technet.microsoft.com/en-us/library/bb123981%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396
http://o365info.com/manage-retention-policy-by-using/
https://technet.microsoft.com/en-us/library/bb738155(v=exchg.150).aspx
Answer is correct. Get-Mailbox | UserMailbox | Set-Mailbox | $null
Answer is:
Get-Mailbox
UserMailbox
Set-Mailbox
$null
https://technet.microsoft.com/en-us/library/bb738155(v=exchg.150)