19. The physicist rightly dreads precise argument，since an argument that is　convincing only if it is precise loses all its force if the assumptions on　which it is based are slightly changed，whereas an argument that is convincing though imprecise may well be stable under small perturbations of its underlying assumptions. （5+）

物理学家恐惧于那些精确无误的论据不无道理，因为某种只有在它是精确无误的条件下才令人置信的论据，一旦它赖于建立其上的假设稍有变化，便会失去它一部的作用；而与此相反，一个尽管并不精确无误但却令人置信的论据，在其基本假设（underlying assumption）稍微受干扰的情况下，仍然有可能是站得住脚的。

难句类型：复杂修饰

解释：本句在文章中就是一个自然段，虽然长度比不上前面第一章中所举的那个长达10行的例子，但是难度绝不在那句话之下。本句堪称句子的大杂烩，连主句带从句居然一共有八个。从大往小说，由 whereas连接了两个大句子，whereas后面的句子中的主语an augument之后又跟了一个定语从句that is convincing though imprecise， 修饰augument。whereas前面共有六个句子，由the physicist作主语的主句；由since引导的原因状语从句，修饰since从句中主语an augument的由that引导的定语从句，此定语从句中的条件状语从句only if it is precise; since从句中的条件状语从句if the assumptions on which it is based are slightly changed,以及修饰此从句中的主语assumptions的定语从句on which it is based一共八个句子，从句套从句，实在令人叹为观止。

然而，在考试现场去数句子的数目，是只有呆子才会干的事，读者们惟一要干的事就是反复阅读这句话，什么时候练到不必去想其语法结构就能按原文顺序读懂，才算初步掌握；再进一步把它读顺，直到你看不出这个句子有什么特别的地方，看上去还挺舒服就算训练成功。

意群训练：The physicist rightly dreads precise argument, since an argument that is convincing only if it is precise loses all its force if the assumptions on which it is based are slightly changed, whereas an argument that is convincing though imprecise may well be stable under small perturbations of its underlying assumptions.

20. However，as they gained cohesion，the Bluestockings came to regard themselves as a women's group and to possess a sense of female solidarity lacking in the salonnieres，who remained isolated from one another by the primacy each held in her own salon. （4-）

起初，蓝袜女们确实模仿了法国沙龙女主人，将男性襄括到其小圈子中来。然则，随着她们获得的凝聚力，她们渐趋将自己视作一女性团体，并拥有了一种妇女团结意识，而这种意识在法国沙龙女主人身上则荡然无存，因为她们每个人在其自己的沙龙中自视甚高而彼此孤立隔绝开来。

难句类型：复杂修饰

解释：本句读到表示并列的连词and开始变难。and之后的不定式与前面的不定式是并列的，to的前面省略了一个与前面一样的谓语came。　 lacking之后的分词作定语修饰a sense of female solidarity其后的由who引导的定语从句又修饰逗号前面的salonnieres此从句中又有一个定语从句that each salonniere held in her own salon修饰其前的primacy,但是由于引导词that在从句中作宾语，因此被省略。

意群训练：However, as they gained cohesion, the Bluestocking came to regard themselves as a women's group and to possess a sense of female solidarity lacking in the salonnieres, who remained isolated from one another by the primacy each held in her own salon.

21. As my own studies have advanced，I have been increasingly impressed with the <I>function</I>al similarities between insect and vertebrate societies and less so with the structural differences that seem，at first glance，to constitute such an immense gulf between them. （5）

随着我的研究不断深入，我对昆虫和脊椎动物群落之间的功能类似性印象愈来愈深刻，而对结构上的差异印象愈发淡漠，虽然这些结构上的差异初看上去似乎构成了二者间一条无法愈越的鸿沟。

难句类型：复杂修饰、插入语、省略

解释：本句子的中间一段impressed with the <I>function</I>al similarites between insect and vertebrate societies and less so with the structural differences容易令人看晕，其中的insect and vertebrate societies and less so with由两个and连接了三个部分，然而它们其实不是同一层次的并列，第一个and实际上是between insect societies and vertebrate societies的一部分，是并列的，而and之后的less so with其实是对于一个完整的表达方式I have been increasingly less impressed with的省略形式，去掉了与前面重复的成分