In old times，man considered lightning to be one of the great mysteries（神秘事物）of nature．In fact a single flash of lightning 1.6 kilometers long has enough electricity to light one million lamps．
    The American scientist，Benjamin Franklin，was the first to suggest that lightning is in fact electricity formed between the earth and clouds high above．It happened in 1752．In the same year，he also built the first lightning rod（避雷针）to protect buildings from being struck by lightnings．
    Modern science has discovered that lightning is very strong and powerful．A lightning between a cloud and the earth may be as long as 13 kilometers，and travels at a speed of 30 million meters per second．Scientists have the opinion that there are about 2000 million flashes of lightning per year．In the United States alone，it kills almost one person per day．
    The safest place to be in during an electrical（电的）storm is a closed car．Outside，one should go close to low ground for cover and not stop under a tree．Also one should stay out of water and away from metal fences．Inside a house people should keep away from open doorways and windows and not touch wires or metal things．

人们在观察、欣赏、认识大自然的过程中，会感到心情舒畅、精神愉悦，会情不自禁地赞叹：“江山如此多娇！”于是怡情雅趣油然而生。这说明（    ）

①自然风光之美会激发人们对大自然深深的爱恋之情    ②大自然之美能给人们带来愉悦和享受

③大自然能给人们带来无限的乐趣                              ④人与大自然是完全和谐的

如图，梯子跟地面的夹角为∠A，关于∠A的三角函数值与梯子的倾斜程度之间，叙述正确的是（　　）

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阅读下面的材料，根据要求作文

    “走钢丝”是人类挑战自我极限的高难度项目。有一个走钢丝的表演家，技术超群，他能在两幢20层高的大楼间，手持一根平衡竿，在钢丝上自由行走。成千上万的人被他令人窒息的壮举吸引。只见他走过钢丝后，让其助手骑在他肩上，准备再走一遍，观赏的人们报以热烈持久的掌声，他示意人们停止鼓掌，然后大声问：“你们相信我和我的助手能走过去吗？”

    “是的，我们相信！”人群狂热地大喊。

    他停了停，然后大声问：“谁愿意骑在我的肩上？”

    人群死一般寂静。

根据你对上述材料理解，自选角度，写一篇600-800字的文章。

【注意】①题目自拟，立意自定；②除诗歌外，文体自选；③不得抄袭、套作；④文中不得出现你所在的学校校名，以及教职工、同学和本人的真实姓名。