You have a netbook computer that runs Windows 7. The computer has a single 30-GB partition that has 10GB of free space. You need to create a system image of the computer by using Windows Backup. You mustachieve this goal by using the minimum amount of time.  What should you do first?（）

• A、Attach an external hard disk.
• B、Attach an external DVD burner.
• C、Convert the local hard disk to a GPT disk.
• D、Create and attach a virtual hard drive （VHD）.