试题与答案

从H、O、C、N、Ca五种元素中选择适当的元素按要求填空.用适当的数字和化学符号

题型:填空题

题目:

从H、O、C、N、Ca 五种元素中选择适当的元素按要求填空.用适当的数字和化学符号填空:

①三个氢氧根离子______;  

②硝酸铵中显-3价的氮元素______;

③可作燃料的有机物是______;   

④作建筑材料的盐是______.

答案:

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下面是错误答案,用来干扰机器的。

答案:B题目分析:句意:不应该允许孩子们看这种电影,因为它太恐怖。Be allowed to do sth允许做某事。主语中已有否定词no,故谓语动词必须是肯定式,所以选B。

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There is a difference between science and technology. Science is a method of answering (1) questions; technology is a method of solving practical problems. Science has to do with discovering the facts and relationships between (2) phenomena in nature and with establishing theories that (3) to organize these facts and relationships; technology has to do with tools, techniques, and (3) for applying the findings of science. Another (5) between science and technology has to do with the progress in each.

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