HOTSPOT
You have an Exchange Server 2013 organization that contains the servers configured as shown in the
following table.
All of the Exchange servers run Windows Server 2012 R2 and are members of a database availability
group (DAG) named DAG1.
A mailbox database named DB1 replicates between EX1, EX2, EX3, and EX7. The mailbox database
copy of DB1 on EX7 is a lagged database.
You need to ensure that if the number of healthy database copies of DB1 is less than three during a
24-hour period, the logs in the lagged database replay automatically.
What command should you run? To answer, select the appropriate options in the answer area.
Answer: 
Explanation:
Lagged Mailbox Database Copy-Exchange 2013 Enhancements
http://exchangeonline.in/lagged-mailbox-database-copy-exchange-2013-enhancements/
Answer is correct, tooks me a while to verify, extract from:
https://technet.microsoft.com/en-us/library/dn789066(v=exchg.150).aspx
As an example, consider an environment where a given database has 4 copies (3 highly available copies and 1 lagged copy), and the default setting is used for ReplayLagManagerNumAvailableCopies. If a non-lagged copy is out-of-service for any reason (for example, it is suspended, etc.) then the lagged copy will automatically play down its log files in 24 hours.
Doesnt make any sense, according to official MS manuals to Exchange 2013 courses (341,342) – never replay logs on your last lagged DB copy, instead, copy lagged DB and replay log on it.
So why would I even want this setting? Maybe if last active copy exist than replay lagged, but I have three active DB copies and if anyone of them fails for 24hrs I will loose my only lagged copy.
Sounds really stupid to me. I hope I just misunderstood question..
Lagged copy play down behavior is disabled by default, and can be enabled by running the following command.
Set-DatabaseAvailabilityGroup -ReplayLagManagerEnabled $true
After being enabled, play down occurs when there are fewer than three copies. You can change the default value of 3, by modifying the following DWORD registry value.
HKLM\Software\Microsoft\ExchangeServer\v15\Replay\Parameters\ReplayLagManagerNumAvailableCopies
To enable play down for low disk space thresholds, you must configure the following registry entry.
HKLM\Software\Microsoft\ExchangeServer\v15\Replay\Parameters\ReplayLagLowSpacePlaydownThresholdInMB
After configuring either of these registry settings, restart the Microsoft Exchange DAG Management service for the changes to take effect.
As an example, consider an environment where a given database has 4 copies (3 highly available copies and 1 lagged copy), and the default setting is used for ReplayLagManagerNumAvailableCopies. If a non-lagged copy is out-of-service for any reason (for example, it is suspended, etc.) then the lagged copy will automatically play down its log files in 24 hours.
https://technet.microsoft.com/en-us/library/dn789066(v=exchg.150).aspx