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10处，多者(从第11处起)不计分。

    Last week，my friends invited me go camping to see the sunrise．I felt so exciting and asked for my parents'permission．Luckily，he agreed．We got to the mountain top that we would stay for a whole night．We were singing together while one of my friends were playing the guitar．The next morning，we wake up at about five o'clock．We could not wait to see the sun to come up．After a while，we saw the red color light up the sky gradual．It was so amazing scenery．The beauty in nature impressed me at that moment．

材料的电阻与温度有关。进一步研究表明：在温度变化范围不太大时，电阻随温度的变化可以近似地表示为如下关系式：R＝R₀（1＋at），其中，R是温度为t时的电阻，R₀是温度为0℃的电阻，a称为电阻温度系数，单位是℃－1，下面列出一些材料在0～120℃的电阻温度系数：

4乘2写作____×____，积是____。