You are the network administrator for your company. The network consists of a single Active Directory domain. All network servers run Windows Server 2003. You are directed to back up all files in a folder named C:\Data on one of the servers. You use the Backup utility to perform a normal backup of C:\Data. When the backup is complete, you review the backup log file and discover the following message: "WARNING: Portions of '\Data\Letter.doc' cannot be read. The backed up data is corrupt or incomplete. This file will not restore correctly." You need to ensure that all documents in C:\Data can be restored successfully. What should you do? （）

A. In the Backup utility, specify an incremental backup. Run the backup again.
B. In the Backup utility, clear the Disable volume shadow copy option. Run the backup again.
C. In the attribute properties of C:\Data\Letter.doc, select the File is ready for archiving option. Run the backup again.
D. In the Offline Settings dialog box of C:\Data, select the All files and programs that users open from the share will be automatically available offline option. Run the backup again.