我们知道，文章由段落组成，段落的发展从主题句开始，段落由展开句组成。所谓的展开句就是在文章段落中阐明主题句的一些句子。
很多人在写英语作文时会遇到这样的问题：不知道怎样写展开句。他们在拿到作文题目后能够很快确定文章的基本结构和主题句，但对主题句（论点）进行论证时却发现写了两三句后就无话可说，导致分析论证流于表面，无法深入。
遇到这种问题时，可以采取下面这几种方法进行扩展：
1.举例法：
举例法是目前议论文写作中最常见，同时也是应用最广泛的一种段落展开方法。通过举例能够让文章内容更加丰富，同时更加具有说服力。
比如，有这样一个作文题目：Governments should not fund any scientific research whose consequences are unclear.
如果你支持题目的观点，可以提出这样的分论点：Being circumspect about research whose objectives are too vague can help us avoid significant opportunity costs. 展开该分论点的一个方法是举例，比如可以列举美国的“星球大战”研究计划的例子：
Being circumspect about research whose objectives are too vague can help us avoid significant opportunity costs. Consider the "Star War" defense initiative championed by the then US President Ronald Reagan during the 1980s. In retrospect, this initiative was ill-conceived and largely a waste of taxpayers' money —— money that could have been devoted to addressing pressing socio-economic problems of the day, such as AIDS, environmental damage, poverty and drug trafficking. As it turned out, at the end of the "Star War" debacle America was drawn into a quagmire of economic recession and social unrest, to the detriment of the nation at large.
使用举例法需要写作者具有一定的素材积累。平时阅读的时候我们要留意收集一些具有一定通用性（即能用于很多题目的论证）同时又有一定的独特性（即没有被用得很滥）的例子。
2.反证法
反证法的思路是“如果不（接受本段的论证点），会（产生什么样的结果）”，通过这样的方式来对问题进行更加深入的思考。举个例子，对于这样的题目：Students should always question what they are taught instead of accepting it passively. 我们可以提出这样的分论点：Students in fields such as law and political science should think critically about current legal systems. 学习法律和政治学的学生应该学会质疑当今存在的各种法律法规的正确性。通过反证法可以进行思路扩展：如果他们不这样做的话，会发生什么，从而提升论证的深度：
Students in fields such as law and political science should think critically about current legal systems. While law students must learn to appreciate timeless legal doctrines and principles, they should continually question the fairness and justification of current laws. Without such skepticism, our laws would not evolve to reflect changing societal values and to address new legal issues brought by new technologies, fox example AI and self-driving cars.
3.分类法
分类法也是段落展开的常见方法。分类法根据事物的特点分别归类，很多东西可以被分成不同的类别，不同的东西也可以被归为同一类。主题句确定后，段落的内容有时可以用分类顺序来组织和发展。比如，同样对于上面的题目：Students should always question what they are taught instead of accepting it passively. 我们可以采用分类法进行展开，即对于不同专业领域的学生（比如物理专业，艺术专业，法律专业），质疑精神对他们来说都同样重要：
