Spending two or three hours playing outdoors each day can reduce(减少)a child’s chance of becoming short-sighted（近视）,research shows . It challenges the belif that short-sightedness is caused by computer use , watching TV or reading in weak light . Australian government researchers believe that sunlight is good for people’s eyes . They compared the vision （视力）and habits of 100 seven-year-old children in China and Australia .In all,30% of the Chinese children were short-sighted .This percentage was ten times higher than Australian children. Both groups spent a similar amount of time reading, watching TV and playing computer games .However , the Australia children spent an average of two hours a day outdoors ,90 minutes more than the Chinese children. Professor Ian Morgan said ,“Humans are naturally long-sighted ,but when people begin to go to school and spend little or no time outdoors ,the number of short-sighted peoplegets larger. We are also seeing more and more short-sighted children in cities all around the world –and the main reason may be that city children spend less time outdoors . Daylight can be hundreds of times brighter than indoor light . But why does playing outside prevent us from becoming short-sighted ? Scientists believe that natural light has a special chemical（化学物质）which stops the eyeball from growing out of shape and prevents people from becoming short-sighted . So go outdoors .It doesn’t matter if that time is spent having a picnic or playing sports . 根据材料内容选择最佳答案，并将其标号填入题前括号内。 小题1:What can reduce a child's chance of becoming short-sighted according to the passage ? A．Playing computer games. B．watching TV. C．Reading books. D．Spending 2 or 3 hours playing outside every day. 小题2:What does the underlined word ' percentage ' mean? A．百分比 B．功率 C．平均分 D．效率 小题3:How much time did the Chinese children spend outdoors according to the research? A．2 hours. B．90 minutes. C．1 hour. D．30 minutes. 小题4:What is the fifth paragraph mainly about? A．Why people become short-sighted. B．Why natural light has a special chemical. C． Why playing outside is good for one's eyesight. D． Why daylight is much brighter than indoor light. 小题5:Which of the following is TRUE according to the passage? A．People will all become short-sighted after they begin to go to school. B．Playing outdoors for 2 or 3 hours every day can help protect your eyesight. C． Children in Australia are more likely to become short-sighted than those in China. D． lf you spend 2 or 3 hours playing outside each day, you will become short-sighted.