短文改错。 

     假如英语课上老师要求同桌之间交换修改作文。请你修改你同桌的以下作文。文中共有

10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏字符号(∧)，并在其下面写出该加的词。

删除：把多余的词用斜线(＼)划掉。

修改：在错的词下画一横线，并在该词下面写出修改后的词。

注意：1．每处错误及其修改均仅限一词；

          2．只允许修改10处，多者（从第11处起）不计分。

     Schools should be clean and pure place. But now something bad happens. Some students cheated

in examinations at school. As students, we often have examinations, many of which are sometime too

difficult for us. In addition, some students not work hard at their lessons. So when taking examinations,

they are dishonest in order that get better results to please his parents and teachers. I think it wrong to

cheat in examinations though it breaks the rules of schools. We students should be honest and try to

get good grades in studying hard instead of by cheating in the examinations. What's more, we should

improve our study methods and get good prepared for examinations.

__________________________________________________________________________________

铁、铝、铜是日常生活中使用最广泛的金属。

（1）上述三种金属中，人类最早大规模冶炼和使用的是____

（2）常温下一些金属的物理性质数据如下：

（3）金属铝与氧化铁在高温条件下能发生置换反应，其化学方程式为                                      。

（4）炼铁的原理是利用一氧化碳与氧化铁反应。在实验室里，可用下图所示装置进行实验：实验中玻璃管内的粉末由红色变为         色，该反应的化学方程式为                                            。