You have an Exchange Server 2010 Mailbox server that contains multiple mailbox databases.You need to ensure that you receive an e-mail alert if the volume that contains the mailbox database files has less than 25 percent of free space. What should you do？（）
- ACreate a new Data Collector Set.
- BCreate a new Event Viewer Subscription.
- CAttach a new task to the Application event log.
- DModify the properties of the mailbox database objects.