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5、Late research shows that yawning helps in keeping the brain cool, contradicting the popular belief that yawning promotes sleep and is a sign tiredness.

     Yawning involves opening the mouth involuntarily while taking a long, deep breath of air. It is commonly believed that people yawn as a result of sleepiness or tiredness because they need oxygen.

     However, researchers at the university of Albany in New York said their experiments on 44 students showed that drawing in air helps cool the brain and helps

it work more effectively.

     They said that their experiments showed that raising or lowering oxygen and carbon dioxide levels in the blood did not produce that reaction. Study participants were shown videos of people laughing, being neutral(正常狀態(tài))and yawning， and researchers counted how many times the volunteers responded to their own ‘contagious yawns’，reported the online edition of BBC News.

      The researchers found that those who breathed through the nose rather than the mouth were less likely to yawn when watching a video of other people yawning. This was because vessels（血管）in the nasal cavity(鼻腔)sent cool blood to the brain.

      The same effect was found among those who held a cool pack to their forehead,

Whereas those who held a warm or room---temperature pack yawned while watching the video.

      ‘Since yawning occurs when brain temperature rises, sending cool blood to the brain serves to maintain optional levels of mental efficiency.’ the authors wrote in the journal Evolutionary Psychology.

1) From the text, we know that ___________________________.

  A) yawning happens to you when your brain temperature rises

  B) Evolutionary Psychology probably is a name of a novel

  C) raising or lowering oxygen and carbon dioxide levels in the blood cause people to yawn

D) people breathing through the mouth rather than the nose are less likely to yawn when watching a video of other people yawning

2) Which of the following is not the one that people usually believe according to the text?

A) Yawning promotes sleep          B) Yawning is a sign of tiredness

C) Sleep-ness or tiredness leads to yawning

D) Yawning helps the brain work more effectively

3) What is the text mainly about?

  A) Cool your brain with a yawn      B) Yawning is natural to you

  C) Yawning is harmful to your brain  D) Yawning is necessary for everyone