If your head is overheating, you are very likely to yawn(打哈欠) soon, according to a new study that has found the main purpose of yawning is to control brain temperature. The study explains several mysteries about yawning, such as why it’s most commonly done just before and after sleeping, why certain diseases lead to too much yawning, and why breathing though the nose often stops yawning. “Brains are like computers,” Andrew Gallup, a researcher in the department of Biology at Binghamton University who led the study, said. “They operate best when cool.” He and his co-workers Micheal Miller and Anne Clark did researches on yawning in parakeets(长尾小鹦鹉) , which have relatively large brains, live wild in Australia, often experience temperature changes, and, most importantly, do not yawn when others yawn, as humans and some other animals do. For the study, the scientists put parakeets under three different conditions: increasing temperature, high temperature and normal temperature. While the frequency(频率) of yawns did not increase under the latter two conditions, it increased greatly when the researchers increased the temperature. It’s now believed yawning operates like a radiator(散热器). If air in the atmosphere is cooler than the brain and body temperatures, taking it in quickly cools blood, which in turn cools the brain. The new findings also explain why tired people often yawn. Both tiredness and sleep loss can increase brain temperature, while yawning can cool down the brain. In the future, researchers may focus more on brain temperature and its role in diseases and their symptoms. But the new study on yawning changes the popular idea that yawns are just signs of getting tired of something. 49. What’s the best title for the passage? A. Why don’t people yawn at normal temperature? B. The yawn explained—it cools your brain. C. Yawning operates like a radiator. D. The cause of yawning—finally found out. 50. The main reason why researchers chose parakeets to do the research is that parakeets______. A. have very large brains B. live wild in Australia C. are not affected by others’ yawning D. experience frequent temperature changes 51. The writer may suggest doing all of the following to stop yawning EXCEPT______. A. breathing through the nose B. turning up the heat C. enjoying some cool wind D. putting a cold towel on your forehead 52. In which section of a newspaper would you most probably read this passage? A. Discovery.        B. Education.         C. Health.              D. Mystery.