拓展句

拓展句拓展句又称扩展句，它以具体的细节或事例的形式拓展深化段落的主段。

拓展句应上承主题句，下启结尾句，在全段中应该占有较大篇幅。

一个段落是由主题句和扩展句共同构成。

扩展句是对主题句的延伸或证明。

它们之间的关系是构成一个段落的好坏的关键拓展句的写作要领拓展句和主题句之间至少要注意以下两点：第一，意义的相关性（unity）；所谓的意义相关性指的是所有扩展句都必须是主题句的延伸或者证明，它对主题句起到支持作用。

否则这样的扩展句就应当删掉。

拓展句的写作应受主题句，由其是主题句中心思想的制约。

因此，不同的主题句体现不同的制约思想。

例如主题句“My choice of traveling by train is based on the following three reasons”在一定的程度上决定着拓展句的写法：首先，拓展句必须写“reasons”，而且是“three reasons”，而不宜写成“two reasons”或“four reasons”；其次，这些“reasons”是“my reasons”，而不是“his/her reasons”；最后，所有的拓展句还要集中在“by train”上，而不是其它交通工具。

因此，这一段落可以这样写：My choice of traveling by train is based on following three reasons (主题句“我选择乘火车游的三个理由”限定本段的范围). Firstly, traveling by train is the safest way of transportation (理由之一“安全”，同时也是层次主题句一). Seldom have we heard of train accident because train runs on tracks and is hardly affected by weather (拓展句—补充说明). Secondly, it is very economic to travel by train (理由之二“经济”，同时也是层次主题句二). Train ticket won’t cost so much as that of air flight, and traveling by train saves much more time than sitting in a bus（拓展句—补充说明）. Finally, it is comfortable to sit in a train which is spacious and offers a good view of the landscape outside the window(理由之三“舒适”，同时也是层次主题句三).第二逻辑的一致性（coherence）只有内容上的相关性还不足以保证能写出好段落。

在行文过程中作者还要注意各个句子的正确、紧凑安排，也就是要保证意义的连贯性。

比如我们有 B、C、D和E四个句子都可以证明A这个主题句，但是它们的位置如何安排呢？那就要根据它们之间的关系以及主题句之间的关系来安排，并且还要有一定的过渡词来体现这种安排。

只有这样，作者写来才会顺理成章，而读者读来也会顺水行舟，没有妨碍。

实现意义的连贯一般采取两种手段：逻辑的连贯和过渡词的使用。

逻辑的连贯就是依靠扩展句自身具有的逻辑关系对句子进行正确的排列所实现的连贯：过渡词的使用就是依靠过渡词表现连贯的意义。

例如：In my opinion, there are two things which have led astray those philosophers that have insisted so much on the selfishness of man (段落主题句将话题集中在两个内容上). In the first place (“首先”—衔接成分—), they found, that every act of virtue or friendship was attended with a secret pleasure; whence (连词) they conclude, that friendship and virtue could not be disinterested (引出某些人对内容一的看法). But the fallacy of this is obvious (转折句). The virtuous sentiment or passion produces the pleasure, and does not arise from it (通过转折过渡到自己对内容一的不同看法). I feel a pleasure in doing good to my friend, because I love him; but do not love him for the sake of pleasure (拓展句—补充说明). In the second place (“其次”—衔接成分二), it has always been found, that the virtuous are far from being indifferent to praise; and therefore（连词）they have been represented as a set of vainglorious men, who had nothing in view but the applause of others（引出某些人对内容二的看法）. But this is also fallacy（转折句）. It is very unjust in the world, when they find any tincture of vanity in a laudable action, to depreciate it upon that the same with vanity, as with other passion（通过转折过渡到自己对内容二的不同看法）…内容层次的连贯一般来说，在段落主题确立之后，通常要分几个层面进行阐述和论证，层次的安排必须符合英语的逻辑，其意义必须连贯。

英语说明文和议论文通常采用下列两种方法：演绎法演绎法也就是先概括出主题思想，然后用事实、例证等分几个层面对主题进行说明和论证。

例如在“TV: A Good Thing Or Bad Thing”一文中，Good thing 指TV has its informative, educational and entertaining function. 然后从Informative, educational, entertaining 三个方面加以论述。

主次递增或递减法这种组织方法是按层次内容的重要程度来安排的，主要取决于作者对层次重要程度的看法。

主次递增法是先讨论或是说明不太重要的内容，依次进入重要或最重要的内容。

主次递减法与此相反，即把最重要的放在前面，依次递减。

例如：Modern whaling techniques have brought the whale population to the threshold of extinction（段落主题句）. In the nineteenth century, the invention of the steamboat increased hunters speed and mobility. Shortly afterward, the grenade harpoon enabled hunters to kill whales quickly and easily from the ship’s deck. 1924, factory ships were designed that could reduce a ninety-foot whale to its by-products in roughly thirty minutes. After World War II, more powerful boats with remote sensing devices gave final boost to the whaling industry. The number of kills had now increased far abovethe whales capacity to reproduce (主次递增法—按时间顺序).There are a few reasons why Mary likes living off-campus better than in a dormitory（段落主题句）. First, she can keep her car at a private house. At campus dorms, there are no parking spaces for student cars. Second, it is easier to study in a private house. A dorm is often too noisy, but a house rarely is. Third, she has more privacy in a house. In a dorm, she has a room all to herself. Finally, a private house costs less. For example, she paid $120 a month to live in a dorm, but it costs her only $90 to live in a private house（主次递减法—把重要的内容放前面）.人类的思维都有一定的规律，既有共性也有个性。

由于上述两种方法比较符合英语国家人的思维习惯，所以用这两种方法拓展英语说明文和议论文的段落比较容易为英语读者所接受和理解。

拓展句写作中的问题在拓展句的写作中，容易犯的错误主要有：跑题、岔题、重复、片面、缺乏必要的过渡词和缺乏逻辑性。

1．跑题：例1：The report indicates that babies of fathers who smoke are likely to be smaller and weaker than babies of non-smoking fathers. Of course it is already well known that pregnant women who smoke can damage the health of their babies. My sister smoked twenty cigarettesa day when she was expecting her first child. Another worrying point is that smoking just before the start of the pregnancy can affect the baby later. I heard recently that certain foods harm unborn babies.在这个例子中，主题句说的本来是父亲抽烟对小孩健康的影响，但是拓展句讲的是未来的母亲抽烟对孩子的影响。