Exchange Backup

I have been asked to answer certain things related to exchange server for furure safety.
I have been given a scenario:-
The Exchange server hosts 500 users and contains

one storage group and one mailbox store. The

size of the mailbox store is 23 GB. Every night,

a full backup is performed on the storage group.

The mailbox store fails. When you attempt to

bring it back online, the mailbox store fails to

mount. You discover that the mailbox store is

corrupted

You need to restore all the exchange mailboxes

without losing any data?

a. Restore the mailbox store and the transaction

log files REPLAY the transcation log files Do

not replay the existing transaction log files

Replay the transaction log files

b. Restore the mailbox store but not the

transaction log files. Do not replay the

existing transaction log files

c. Restore the mailbox store but not the

transaction log files. Replay the existing

transaction log files

d. Restore the mailbox store and the transaction

log files. Delete the restored transactio log

files


I think c.

Once I was asked in interview that shall disaster recovery bring the complete data. Suppose Admin takes a full backup sunday. Incremental on Monday and Tuesday. Wed differential and Thursday Incremental. Now one of a sudden the server crashes how can the complete data be recovered. I said no disaster recovery cannot. I said one should insist on the Wed data backup and Thursday data cannot be recovered. What does DR basically do how does it function?