You have an Exchange Server 2010 server named Server1. Server1 has a single mailbox database named DB1 that contains 300 mailboxes. You need to ensure that a warning message is issued when a mailbox exceeds 2 GB. The solution must use the minimum amount of administrative effort. What should you do（）？
- AFrom the properties of DB1， configure options on the Limits tab.
- BFrom the properties of each mailbox， modify the storage quotas.
- CFrom the properties of Server1， configure options on the Messaging Records Management tab.
- DFrom Managed Default Folders， modify the properties of the Entire Mailbox managed folder.