You are a network administrator for ExamSheet.net’s Windows 2000 network. Your computer has Windows 2000 Professional installed. Your office has a power utage while you are running the Windows 2000 disk defragmenter. When you restart your computer， you receive the following error message： "Bad or missing operating system". You want your computer to start properly. You want to do this with least amount of administrative effort. What should you do？（）

A. Reinstall the operating system
B. Start the computer by using the Windows 2000 Professional CD-RO
C. Use the Recovery Console to repair the Master Boot Record.
D. Use the Emergency Repair Disk to repair the Master Boot Record.