You have a portable computer that runs Windows 7. You configure the computer to enter sleep mode after10 minutes of inactivity. You do not use the computer for 15 minutes and discover that the computer has notentered sleep mode. You need to identify what is preventing the computer from entering sleep mode.  What should you do?（）

• A、At a command prompt， run Powercfg energy.
• B、At a command prompt， run Systeminfo /s localhost.
• C、From Performance Monitor， review the System Summary.
• D、From Performance Information and Tools， review the detailed performance and system information.