What should you create first?

You have an exchange server 2016 organization. The organization contains a Mailbox server named EX01.
EX01 contains a mailbox database named DB01.
The volume that contains DB01 fails.
You need to perform a dial-tone recovery of the database.
What should you create first?

A.
a new Recovery Storage Group

B.
a new mailbox database

C.
a mailbox move request

D.
a mailbox restore request

E.
a lagged database copy

Explanation:
https://technet.microsoft.com/en-gb/library/dd979810(v=exchg.150).aspx