article: Want a good night's sleep? Then turn off your computer, cell phone or PSP two hours before you go to bed.
  These things have bright lights. When our eyes see bright lights just before sleep, our sleep patterns   change, a study has found.
  Our body clock starts shutting us down for bed at 9 or 10 pm. But bright lights make our minds think that it is still daytime. That wakes us up and leaves us sleepless, experts say.
  But if you read a paper book before sleeping, you won't have this problem. This is because light from a bedside lamp   does not go straight into our eyes.
  Also, if you are watching a television from across the bedroom, you won't have problems falling asleep. The TV sends light to us from a distance, so the light won't be as strong.
question: Why can't we sleep well if we use a computer before bed time?
options: We think it is daytime if we leave computers on. We feel too excited to sleep after using computers. Lights from computers are brighter than other lights. Lights from computers can change our sleep patterns.