比较说明:我们班的一对孪生姐妹-Twin Sisters in Our Clas.

我们班的一对孪生姐妹
【内容提示】
你们班上有两位同学在很多方面都很相似，她们是一对孪生姐妹。请你选择她们最突出的三个方面的相同点作一比较，写成一篇比较说明的短文。
【作文示范】
Twin Sisters in Our Class
Li Bao and Li Bei are twin sisters in our class. They look very much alike. But they are different in character. The former is an introversive①girl; the latter extroversive②in doing things. In spite of this, they have many same points.
The two are good at studies. They come, to school early every day. Before classes they read English or Chinese texts and often recite good articles or poems. In the classes they listen to the teachers attentively.
When the teachers ask questions, they are always active in answering them. After school they carefully do their homework. If they are not clear of something they ask the teachers or classmates for help. They never let off any problems that they do not understand. So they always achieve excellent marks in examinations.
They both like to help others. On the buses they offer their seats to the old. In the streets they support the blind across the roads. At home they help the parents with housework. In the school they like to do something  for the teachers and schoolmates. Once Mr. Liu moved his house,the twin sisters carried what they could for the teacher till late in the evening. Last term I caught a bad cold and stayed in hospital. Li Bao and Li Bei delivered the meals from my home to the hospital in turn. Because of these they are praised by everybody in our school.
Both of them have a preference for③ singing and dancing. After classes in the afternoons they often take part in singing and dancing activities. So they both sing beautifully and dance well. When there is a partv held in our school they are certainly actresses. As soon as their performances come to an end, people would respond with warm applause. Whenever a classmate holds a birthday party the twin sisters must be invited to give performances. And they both never refuse to be present. Of course they would sing sweet songs or offer fine dances.
Those are the same points the two sisters share. Do you think that they are twins worthy of the name?
【词语解释】
①introversive[?intr+u＇v+:siv] adj．内向的
②extroversive [?ekstr+＇v+:siv] adj．外向的
③have a preference[＇pref+r+ns] for偏爱……，特别喜爱……
【写法指要】
这是一篇比较型说明文，即谈论两个人或事物的相同点的文章。写这种文章时，在引言段要首先指出二者的不同点，然后将篇题落在二者的相同点上。这样，在扩充段中分别具体详细地说明二者的相同点。本文的篇题句是“… they have many same points.”。三个扩充段的主题句都是段落开头的第一个句子。