You work as the enterprise exchange administrator at Company.com.The Company.com network consists of a single Active Directory domain named Company.com.Company.com has an Exchange Server 2010 organization.Company.com contains an exchange server 2010 mailbox server named -sr10.quite a few mailbox databases reside on -sr10.you have received instructions from the cio to set an alert on the volume of the mailbox database files， if the free space is less than 20%.What should you do？（）

• A、The best option is to set up a new Event Viewer Subscription.
• B、The best option is to set up a new Data Collector Set.
• C、The best option is to attach a new task to the Application event log.
• D、The best option is to change the properties of the mailbox database objects.