A、It conserves battery power. B、It lets your laptop rest. C、It makes your laptop easy to control. D、It replaces screen saver. A

There are many computer users who are wondering if they should be putting their computers to sleep at the end of the day or if they should actually shut down. Sleep mode was originally implemented simply as a screen saver. On laptop computers it became very useful for conserving battery power if the computer was to remain idle for a period of time. (In the beginning, sleep mode was for laptops only.) Later, the monitor companies got on the "green" computing kick, and began to build in "energy saver" features that would put just the monitor to sleep, but not the computer. So now the purpose of the desktop’s Sleep became a) to conserve power, and b) to let the computer "rest."
    Putting your computer to sleep at the end of the day has these two very advantageous benefits. First and foremost, the sleep mode allows your computer to go to sleep when not in use, and to re-launch very quickly. A cold startup will take as much as 10 times as long. That’s the most important function. It also allows you to leave projects in progress like they are, and reappear instantly when you return.
    There is a downside however. So some warnings are in order. As Mr. Murphy put it: "If something can go wrong, it will." If anything happens during the period of sleep, you can come back to a crashed computer, and any unsaved work gone forever. For instance, around here I can’t leave the computers at sleep during a thunder storm season--in a black-out, without battery back-up, you’ve got a crash.