（1）农作物在生长的过程中，因体内缺少某些元素，会使叶片发黄，请仔细观察上面的两幅图，并回答问题．它们都变黄，但有所不同，左侧叶边发黄，缺的元素是①____；建议右侧图叶片发黄应使用的化肥的作用②____；

（2）氯化钠可做融雪剂的原因是____ ；

（3）用化学方程式表示下列反应：

①钟乳石、石笋的形成____ ；

②碳酸钙可以做补钙剂的原因____ ；

③氢氧化钠密封保存的原因____ ．

    In Western countries, many children do chores to get pocket money. 1 usually start to do this at the age of 10.

    School students have to do homework and study 2 tests on weekdays. So they often do chores on 3. Some young kids only do 4 chores. So they don't get much money. But that's all right. Many of them only want to 5 candies. And candies are cheap！They help wash the dishes after dinner, and 6 the family cat or dog.

    When kids get 7，they want to buy more and more things. They want things that are more expensive than candies. Then they have to work harder！They often 8 the family car, cut the grass, walk the dog or cook dinner.

    Doing chores is a good 9 for kids to learn new things. For example, they can learn how to use a lawn mower(割草机) or 10 to cook. Of course, their parents help them at first.

阅读下列图文材料，回答问题。

材料一 孟加拉湾是风暴潮的多发区，也是风暴潮的重灾区。图为某季节孟加拉湾风暴潮爆发情况图。

材料二 中央台消息：国家海洋环境预报中心2007年3月3日（农历正月十四）发布风暴潮、海浪一级紧急警报。受强冷空气等的影响，渤海将出现1969年以来最强的一次风暴潮