黑龙江最大的火山湖镜泊湖，冬季捕捞创造过一网打鱼86万斤的记录．捕捞时，在厚约1米的冰面上开一个进网口和一个出网口，两口相距1500米，捕捞所用的渔网，长约1500多米，宽约800米，网到冰下水中后，要在广泛的湖中展开，还要准确地在出网口收拢．关于网头上的设置，以下说法正确的是（    ）

下列各种摩擦中，属于有害摩擦的是____ ；属于有益摩擦的是____ ．

（1）机器运转时，各部分之间的摩擦；     （2）拔河比赛时，手与绳子之间的摩擦；

（3）自行车行进时，后轮胎与地面摩擦；   （4）吃饭时，筷子与食物之间的摩擦．

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。

    I am writing to ask for whether you are able to do me a favor. I want to have a pen pal, hopefully a girl in the early twenties, and with interests similarly to mine. In my mind, he is someone interesting in traveling, swimming, and playing table tennis. Beside, it will be better for her to have a pet dog as I have been keeping one at home for some time. With such pen pal, I hope I can share with her my experiences in traveling, taking care of pets, or whichever we have in common. I believed I will improve my English by doing so and learning more about her country. I am looking forward to hearing from you soon.