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假如没有台风和闪电
       ①人们不喜欢台风,也害怕闪电。但是,在这个世界上,如果没有了台风和闪电,又将怎样呢?
       ②假如没有台风,全世界本已严重的水荒就会更加严重。台风能为人类送来大量的淡水资源。据测算,一个直径不太大的台风,登陆时可带来近30亿吨降水。每年,台风给中国、日本、印度、菲律宾、越南以及美国沿海地区带来的水量,往往要占到当年降水量的25%以上。在炎热的季节里,台风暴雨的光临,可以缓解旱情,使作物焕发生机。
       ③假如没有台风,世界各地冷热将会更不均衡。赤道地区日照最多,气候炎热。台风最大时速可达200千米,如果没有台风来驱散、带走这一地区的热量,热带便会更热,寒带也会更冷,而温带将从地球上消失。
       ④假如没有闪电,人类将失去一位勤奋的“清洁工”。雷电交作时,空气中的部分氧气会激变成臭氧。稀薄的臭氧不但不臭,而且能吸收大部分宇宙射线,使地球表面的生物免遭紫外线过量照射的危害。闪电过程中产生的高温,又可杀死大气中90%以上的细菌和微生物,从而使空气变得更加纯净,更加清新宜人。
       ⑤假如没有闪电,人类就将失去一座巨大的“化肥厂”。据估计,每年地球上空会出现31亿多次闪电,平均每秒钟100次。每次放电,其电能高达52700千瓦时,连世界上最大的电力装置都不能和它相比。空气中含有占总体积78%的不能被作物直接吸收的氮气,闪电时,电流高达10万安培,空气分子在瞬间被加热到3万摄氏度以上,致使大气中的氮和氧化合,生成一氧化氮;一氧化氮继而转化生成二氧化氮;雨水又与二氧化氮反应生成硝酸;含有微量硝酸的雨水降落地面后即是作物可以直接吸收的氮肥。据测算,全球每年由雷雨(闪电)“合成”的氮肥达5亿吨。这5亿吨从天而降的化肥,相当于5万个年产1万吨的化肥厂的产量总和。
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    Your junior high school years are coming to an end. After the big exam, most of you will go on to study in a senior school. What are you   expecting from senior high school? Let's hear some teen readers talk about it.
Zhou Zhijie, 15, from Shanghai:
    I have heard that although Senior 3 is a hard year, Senior 1 and Senior 2 are less stressful. I hope there'll be time then to enjoy sports. There will be plenty to see. Especially, the World Cup in Brazil is coming. We can watch football matches. I'm sure I'll really enjoy it.
Jin Xi, 16, from Harbin, Heilongjiang:
    I really enjoy science. I visit many science exhibitions. I am interested in UFOs, too. I'm crazy about making model planes, although I'm not very good at it because I don't really have enough scientific knowledge. I'll be learning more science in senior high school. In a word, sometime in the future I'm going to build an excellent model plane!
Wang Yaling, 15, from Xiamen, Fujian:
    I hope I can be taller in senior high school. I'm only 155cm. Many people grow faster in senior and I hope I will, too. I want to be 162cm. But I'm not sure about that, since most girls in my family don't grow taller than 160cm. I hope I'm different.
Zhang Fang, 15, from Hebi, Henan:
    I expect that I'll make more friends in senior high school. I study in a middle school in the country. Most of my classmates live nearby. In senior high school, I'll meet different people from different areas. I hope I can learn new things from them.
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