文章无论何种文体，通常都有主题。主题也叫主题思想，通常指文章的主旨和写作目的，它是写作内容的核心。记叙文围绕作者着重记叙的事件, 说明文围绕作者重点说明的对象, 议论文围绕作者的观点来展开主题。同样，每一段也要有中心句来体现该段的主要意思。此外，文章的标题也可以是画龙点睛之笔，或直接点明文章的主旨，或“故弄玄虚”引发读者的兴趣。

主题在不同的文体中是如何具体体现的呢？下面以Teens上学期的几个文段为例，为大家提供一些参考。

Passage 1 (第314期 P4 )

Are you a fan of QQ zone? What does your QQ zone look like?

A survey shows that 90 percent (百分之……) of junior high school students use QQ. Many of them have a QQ zone, too.

A QQ zone is like a blog, but you can do more things with it. You can write a diary and put your photos up. You can also play games and listen to music. To make your QQ zone more beautiful, you can add pictures to it.

QQ zone is a space for students to show off. Boys write jokes and travel diaries. Girls share their photos and play games.

◆点拨：第三段的首句是中心句，后面举例说明我们可以在QQ空间上做些什么。第四段的首句也是中心句，后面用男孩和女孩分别喜欢在空间中做什么来说明QQ空间是学生们的“炫耀之地”。总之，举例说明是一种常用而有力的表现主题的方法。

Passage 2 (第318期 P3 )

Get your feet wet for science

Nicole Preston is an 11-year-old kid from the US. She had an interesting week last month.

Preston, along with some of her classmates, joined in a fun project. The project teaches kids about nature (大自然). Workers for the activity took the students to the Grand River. They tested the health (健康) of the river water.

Students picked up some rocks in the river. Then they cleaned the creatures (生物) off of the rocks and put them in different buckets (桶).

“There are a lot of creatures in that river. It’s amazing,” said Preston. “Teachers say ‘The more creatures there are in a river, the more healthy the river is.’ So the water there is good.”

◆点拨：这是一篇关于美国学生走进大自然，检测河流“健康”状况的文章。标题Get your feet wet for science能够引发读者的兴趣，让读者想要了解为什么要让“脚湿了”才能学到知识，很生动地体现了文章的主题。

Passage 2 (第322期 P5 )

Don’t forget to leave a tip!

In the US, we have a tradition of “tipping ”(付小费). Waiters, taxi drivers, door people … anyone with a service (服务) job can get a tip. Usually, a waiter gets 15-20 percent of the total bill (总额).

My father is a taxi driver in San Francisco. Taxi drivers can get a tip of about 20 percent of the fare (费用). In his 35 years of driving a taxi, my father can even tell a “good tipper” from a “bad tipper” when they sit down in his car.

It is very rude (无礼的) not to leave a tip in the US. So, if you ever go to the US, don’t forget to tip!

◆点拨：这是一篇介绍美国小费文化的文章。文章的第一段第一句直截了当阐明了“在美国付小费是一种传统”这一主题。第二段作者用她父亲的例子更加生动地介绍了美国的小费文化。