article: In today's world, sleep experts say that for a better night's rest, Americans should turn off their smartphones or iPad before sleeping. Such electronic products make the brain more active, and then influence their sleep. But according to a latest survey, more than 90% of Americans regularly use a computer or some other kinds of electronic products in the hour before bed.
  Researchers are finding that man-made light from some electronic products at night may reduce the brain chemicals  that help sleep. The researchers showed that sitting in the light from computer tablets clearly lowered levels of the chemical which manages our body clocks and plays a role in the sleep cycle.
  In the study, the researchers let volunteers read, play games and watch movies on a tablet for different time while measuring  how much light their eyes received. They found that two hours of sitting before a bright tablet screen at night reduced the sleep chemical levels by about 22%.
  Studies of students using computers at night have got the similar results. And researchers say _ may not only cause sleeplessness, but also raise the risk of obesity , diabetes  and other diseases.
  To be on the safe side, the researchers advise us to use computers less before bed, or at the very least turning down your screen as much as possible.
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question: How may electronic products influence people's sleep?
options: Make our brains more active. Make our body weak. Lower our brains' chemicals that help sleep. Change our body clocks.