You need to enable the Litigation Hold feature for each mailbox

Your company has 100 user mailboxes. The company purchases a subscription to Office 365 for
professionals and small businesses. You need to enable the Litigation Hold feature for each mailbox.
What should you do first?

A.
Purchase a subscription to Office 365 for midsize business and enterprises.

B.
Enable audit logging for all of the mailboxes.

C.
Modify the default retention policy.

D.
Create a service request.