scribbling and littering，making our school a dirty and unpleasant place to study in.(现在分词作状语)

I am writing to draw your attention to some improper behavior among us students on our campus：scribbling and littering，which makes our school a dirty and unpleasant place to study in.(which引导非限制性定语从句)

2．很显然学生到处乱涂乱扔是不合适的。

Students tend to litter and scribble about，and it is clearly an improper behavior.(并列句)

It is clearly not appropriate for students to litter and scribble about.(it作形式主语)

3．我相信如果老师和学生共同努力，我们的学校会在不久的将来成为一个更怡人的地方。

I believe that our school will surely become a more enjoyable place in the near future if both teachers and students are willing to work together.(if条件状语从句)

I believe that，with the joint efforts of both teachers and students，our school will become a more enjoyable place in the near future.(with＋n.)

Dear Mr Headmaster，

　　I am Li Hua，a student from Class 1，Senior Ⅱ.I am writing to draw your attention to some improper behavior among us students on our campus：scribbling and littering，which makes our school a dirty and unpleasant place to study in and does great harm to the image of our school.I always feel ashamed whenever I see this.

　　It is clearly not appropriate for students to litter and scribble about.I wonder if the school could place more dustbins around and set up specific rules against such behavior.At the same time，students should be encouraged to develop good habits and better behave themselves.

　　I believe that，with the joint efforts of both teachers and students，our school will become a more enjoyable place in the near future.

　　Thank you for your consideration.

Yours faithfully，

Li Hua