Chapter 12 Sentences
一篇科学论文是由一系列互相嵌套的故事构成，而最小的故事单元则是“句子”。
英文中每一个句子都需要主语，动词，宾语齐备。主谓宾的句子结构可以对应于OCAR的故事结构：主语——Opening;动词——Challenge/Action;宾语——Resolution。
一句话既可以采用OCAR的故事结构，也可以采用LD的故事结构。不过，对于短句子而言，结构的变化空间较小，通常采用OCAR格式。对于长句子，LD结构则更能够抓住读者的注意力。
对于一句话而言，最重要的是“主旨”（topic）和“重点”（stress），它们分别对应开局和落尾的位置。位置不同，会导致一句话表达的意思千差万别，比如下面的几个例子：
A. Viruses were not studied in the sea until 1989 yet are its most abundant biological entities.
B. The most abundant biological entities in the sea are viruses, yet they were not studied until 1989.
C. The most abundant biological entities in the sea were not studied until 1989: viruses.
“its most abundant biological entities”， “ they were not studied until 1989”， “viruses”分别代表了以上三句话所传达出来的重点。可见，即便基本的信息一样，但以不同的结构去表述一句话，所讲的故事可能完全不一样。
所以，对于一句话而言，讲好故事的关键在于“位置”。再参看以下例子：
A. Net mineralization represents the nitrogen available to plants because it reflects the difference between microbial nitrogen release and uptake in soil.
B. The amount of nitrogen available for plants is controlled by net mineralization — the difference between microbial nitrogen release and uptake in soil.
C. The amount of nitrogen available for plants is controlled by the difference between microbial nitrogen release and uptake in soil.
D. The amount of nitrogen available for plants is controlled by the balance between microbial nitrogen uptake and release in soil; we define this balance as net N mineralization.
第一句是针对专业读者的写法，开局就使用专业词汇；第二句为了降低阅读的要求，将“net mineralization”移到了不太重要的中间部位，这样非专业读者也能够一下子就明白所要表达的主旨；第三句更进一步，直接去掉了“net mineralization”，但一点都不妨碍读者理解大意；最后一句，将“net mineralization”移到了最后，这句话的故事就变成了特意解释并强调该专业术语。
从以上的例子，我们可以看出，一句话中的“位置”的重要性排序是：2-3-1，即想要强调的重点在句子的最后（resolution），开头次之（opening），中间最弱。所以，讲好一句话的小故事的关键在于，将合适的信息放在合适的位置。
以上是主要的规律，具体而言，还需要注意一些句子的组织技巧。
比较以下两种写法：
A. The pooled effect sizes, both with and without adjustment for environmental risk factors, were larger for DNA-based than RNA-based viruses.
B. The pooled effect sizes were larger for DNA-based than RNA-based viruses, regardless of whether environmental risk factors were adjusted for.
第一句的主语和动词之间插入了一个不短的限定句，明显降低了可读性。它指示出一个重要技巧：主语和动词要紧密相连，这样可以增加句子的力度。
对于一个句子而言，常见的没能讲好一个小故事的原因有：1. 没有主旨（topic）；2. 没有重点（stress）。
试看这个例子：
A. It has been predicted that the global average temperature will increase at a rate of 0.2˚C/decade.
这句话有两个意思，“It has been predicted”和“global average temperature will increase at a rate of 0.2˚C/decade”，谁是主旨呢？
这样一改，主旨就非常明显了：
B. Global average temperature has been predicted to increase at a rate of 0.2˚C/ decade.
以下例子展示了重点不够凸显：
A. The data did not support our initial hypothesis, as no clear trend in reaction rate with pH was observed.
“was observed”被放在了重点位置，但不是想要表达的重点。
正确的写法应该是这样的：
B. The data did not support our initial hypothesis, as there was no clear trend in reaction rate with pH.
“no clear trend in reaction rate with pH”才是真正的重点。
所以，写好一句话的小故事的要点在于，第一要清晰简短地表述主旨，第二，动词要紧随主语；第三关键信息要放在“重点位置”。