How should this configuration be modified to stop delivering Zero Day malware attacks?

Refer to the exhibit.

How should this configuration be modified to stop delivering Zero Day malware attacks?
A . Change Unscannable Action from Deliver As Is to Quarantine.
B . Change File Analysis Pending action from Deliver As Is to Quarantine.
C . Configure mailbox auto-remediation.
D . Apply Prepend on Modify Message Subject under Malware Attachments.

Answer: C