Recently we have had a heated discussion on whether people should keep pets at home in cities. Some students think it’s a good idea to keep pets because many old people who live alone at home can get some comfort from pets. Besides, getting along well with animals will make our life interesting. On the contrary, the other students are against the idea. In their opinion, if too many people keep pets at home, it is bad for the environment. What’s worse, pets may make too much noise and even attack people.

这是篇正反观点对比的书面表达。在写作时，常使用一般现在时。写作格式一般是：提出问题→两种不同观点→对两种不同观点的论据（理由）逐项作对比。写作方式一般采用集中比较。

文章内容一般由三部分组成：topic sentences：要针对题目要求提出论点。 supporting sentences：展开。concluding sentences：结论。