防雷元件、器件的选用原则是什么？

按照污染物在水环境中的输移、衰减的特点，一般利用水质模型进行预测评价的污染物种类有（）。

A．持久性有机物

B．非持久性有机物

C．酸和碱

D．废热

贴敷法可用于

A．宫颈癌
B．外阴炎
C．痛经
D． * * 炎
E．乳腺炎

第二节读写任务 (共1小题,满分25分)

阅读下面的一封信，然后按照要求用英语写一篇150词左右的回信。

Dear Abby,

Last month my son was told that he no longer has to attend weekend classes at his school.  Since then he spends his weekends going out with his friends to play sports or watch movies.  When he is at home all he seems to do is surf the Internet or play silly computer games. I really think he is just wasting his time having fun when he should be studying. I sometimes ask him if he has homework or extra study to do, but he always says that he has already completed it all. This change makes me very worried. I feel that this free time is encouraging him to be lazy. He isn’t studying long enough and this will reduce his chances of getting into university. I also think it will cause problems when he begins to work because he will not be able to concentrate well and will think more of having fun than his job. I have considered going to the school principal and asking him to change their decision but my son says if I do so his classmates will laugh at him. I don’t want to embarrass my child but I don’t want him to fall behind either. 

Please help.

Concerned Mum

[写作内容]

假设你是信中的Abby，准备给这位母亲回信。以下是回信的内容（信的开头和结尾已经为你写好）：

1．以约30个词概括你所阅读的这封信的主要内容；

2．以约120个词提出你的观点和建议，并包括如下要点：

(1) 你读信后的感受；

(2) 你对信中所述现象的个人观点；

(3) 你对这位母亲的建议。

[写作要求]

1．信中可使用自己的亲身经历或虚构的故事，也可以参照阅读材料的内容,但不得直接引用原文中的句子；

2．信中不能出现真实姓名和学校名称。

[评分标准]

概括准确，语言规范，内容合适，篇章连贯。

下列哪一项未被列为癌前病变（）

A.皮肤过度角化

B.萎缩性胃炎或慢性胃溃疡伴肠上皮化生或不典型增生

C.乳腺囊性增生伴上皮增生

D.子宫颈慢性炎伴鳞状上皮化生及间变

E.皮肤或黏膜的 * * 状瘤、黏膜白斑

简述进行车轮定位前需对车辆做哪些准备工作。