短文改错

     假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写得以下作文。文中共有十处语言错误，每句中最多有两处，每处错误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（^），并在该词下面写出该加的词。

     删除：把多余的词用斜线（\）划掉。

     修改：在错的词下划一横线，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.只允许修改十处，多者（从第11处起）不计分。

Dear friends,

     It is real a good chance to have met all of you here. We have spent several precious weekends learn

in the English Club. Although we have been member for a short period of time, we have made a great

progress. That is because we are all very much active and the activities are not only enjoyable and also

helpful. Besides, the foreign teachers here work hard and try his best to make the activities lively and

interested. I am very pleased to say that all of us greatly improved our spoken English so far. I am looking

forward to see all of you again in the near future!

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裂解反应的四个特点是什么？