A、The rapid development of laptops. B、The benefits of having a laptop. C、Right position before a laptop. D、How to keep a laptop

Sales of laptop computers passed desktops in the U. S. for the first time ever this fall, according to market-research firm IDC. But that’s bad news for backs, necks and shoulders. "Theoretically, laptops are not healthy for human bodiesunless you’re 2 feet tall," says physician Norman J. Marcus, a muscle-pain specialist in New York City.
    (26) When you work at a computer, the keyboard should be at elbow height, so your upper and lower arms form an angle of 90 degrees or more and your forearms are supported by armrests. The monitor should be roughly at eye level so you can lean back in a chair with back support. But most users simply set their laptops on a desk or table. The keyboard is too high, which makes your arms reach up, your shoulders hunch and your wrists bend down. The monitor is too low, which pulls your head and neck forward and down and puts a strain on your back.
    That’s OK if you use your laptop occasionally, for short periods. (27)But if you use one for hours at a stretch--as do millions of college students, business travelers, telecommuters, video-garners and growing numbers of office workers--you’re setting yourself up for muscle problems that can make your entire upper body hurt.
    A wrong position can cause pain and stiffness in the neck, shoulders, back and arms, as well as headaches. (28) There are simple ways to make a laptop healthier. And the key is to separate the keyboard and the monitor, so each can be placed at the proper height.