You are a network administrator for your company. The network contains a Windows Server 2003 computernamed Server3. Server3 functions as a file server. Six users in the accounting department use an accounting software application to open files that are stored in a shared folder on Server3. The users keep these files open for an extended period of time. You need to restart Server3. You need to find out if any files on Server3 are open before you restart the computer. What should you do? （）

A. Use Computer Management to view existing connections.
B. Use the netsend command to send a message to all domain members.
C. Use Task Manager to monitor processes started by all users.
D. Use System Monitor to monitor the Server object in Report view.