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：
The value of skepticism can be illustrated by examples from various fields of study. For students in the field of physics sciences, the ability to question what they are taught is essential. History has seen many physics students, for example Copernicus and Galileo, who queried what they had been taught, thereby paving the way for innovations, invention and discoveries. For art students, it is often bold challenge to established styles and forms, rather than subpar mimicry, that enables them to produce genuinely new art. Even in fields such as law and political science, students must think critically about current legal systems; otherwise, exploitation, tyranny, and prejudice go unchecked.
4.因果法
因果法是论述类文章中最常使用的方法，因果法用于说明事物发展的原因和结果，可根据结果分析原因，也可以由原因推导结果。因果法非常适合用来扩展思路。如果你文章写到一半觉得无话可说，记得多想想“原因和结果”：是什么原因导致了现在正在描述的现象？现在描述的现象又会导致什么样的结果？把这两点想清楚，文章思路就有了。比如上一篇推送里面我们分析的一篇文章：People believe that using mobile phones and computers to communicate makes us lose the ability to communicate with each other face to face. To what extent do you agree or disagree?
如果我们持同意态度的话，会得出这样的主论点：Using mobile phones and computers to communicate makes us lose the ability to communicate with each other face to face.
确定了论点之后，我们可以用“因果法”来展开：为什么使用手机和电脑会降低人们的面对面沟通能力？造成人们面对面沟通能力下降的因素有哪些？这些因素会导致什么样的结果？
仔细分析之后不难得出下面两条结论：
1）很多人在使用电脑或手机聊天的时候很难保持专注，因为他们会受到大量的信息干扰（比如手机推送的新闻和游戏信息等）。习惯了网络聊天的人注意力持续时间会变短，谈话的时候容易分心，这会对他们在现实生活中的交流造成障碍。
2）不少人习惯了在网络聊天中使用各种流行语和缩写，但这些网络流行语往往难登大雅之堂。如果这种习惯被带到现实生活中来，就会给人造成不好的印象。
因此可以这样展开：
Smart phones and computers could in many ways hinder our face-to-face communication skills. Take conversational behaviour. Heavy users of such electronics often have a short attention span and are more likely to jump from topic to topic when an idea springs to mind. As a consequence, they may become unfocused and sidetracked during offline conversations. Internet slang also does its bit. Today, youngsters who text with abbreviated forms of words tend to speak with the same acronyms and use internet catchphrases heavily. These forms of talking are often construed as flighty and uneducated, from which misunderstandings ensue.
在实际写作中很少将一种方法运用到底，一般都是将上面多种方法结合，例如反证+举例，因果+举例，分类+反证等，这样论证效果会更好。
同时，为了使展开句写得顺畅连贯，我们还要留意连接词的使用，例如：
转折关系：while, yet, but, however
并列关系：and, also, likewise
让步关系：though, although, despite, in spite of
递进关系：moreover, what is more, furthermore, in addition, besides
写作是思考的反映，经历什么样的思考就会写出什么样的文章。因此，要真正写好一个段落一篇文章，除了采取以上几种方法之外，还要学会训练自己的思考能力，对日常发生的大小事件、别人的观点，要多从不同层面思考它们的前因后果、成立的前提、适用的领域等，让写作水平和思维能力同步提升。
