【分析】句子主干是由divides...and...(使……对立)搭配连接而成。两个those后面的分词短语作定语修饰those。句子主干为：An invisible border divides those and those.

　　【翻译】一种看不到的鸿沟，把那些主张为了学生有更好的职业前景而把电脑引入课堂的人和那些主张为了获得彻底教育革新更广泛理由而把电脑引入课堂的人的观点对立起来。

　　Very few writers on the subject have explored this distinction——indeed, contradiction——Which goes to the heart of what is wrong with the campaign / to put computers in the classroom.(1999年真题)

　　【分析】句子主干为：Very few writers have explored this distinction. “on the subject”介词短语作状语修饰“very few writers”,“which goes to the heart of what is wrong with the campaign to put computers in the classroom”是定语从句修饰“this distinction”的。

　　【翻译】很少有作者在这个问题上去探究这种差异，实际上，他们是互相矛盾的。而这种差异正是探究把计算机引入课堂运动问题的关键。

　　But, for a small group of students, professional training might be the way to go since well-developed skills, all other factors being equal, can be the difference between having a job and not. (1999年真题)

　　【分析】本句不难，重在对since引导从句的理解，这里since是表示因果关系的连词，表示“因为……”，诸如此类比较隐蔽的因果关系的连词还有as, as表示原因,可译为“由于，鉴于”，如：As he was not well, I decided to go without him(因为他病了，我决定一个人去)。

　　【翻译】但是，对于一小部分学生而言，职业培训也许是一种很好的途径，因为，在其他条件相同的情况下，拥有良好的技能对他们找工作结果的影响是不一样的。

　　The fact / that the apple fell down toward the earth and not up into the tree / answered the question / he had been asking himself about those larger fruits of the heavens, the moon and the planets. (1999年真题)

　　【分析】句子主干：The fact answered the question.“that the apple fell down toward the earth and not up into the tree”，“he had been asking himself about those larger fruits of the heavens, the moon and the planets”分别是the fact和the question的同位语，对其进行说明。

　　【翻译】苹果向下落到地面而不是向上飞到树上，这一事实回答了他长期以来一直对天空中更大天体——月球和行星所存在的疑问。

　　It is entirely reasonable for auditors to believe that scientists / who know exactly where they are going and how they will get there /should not be distracted by the necessity of keeping one eye on the cash register while the other eye is on the microscope. (1999年真题)

　　【分析】句子主干为：It is entirely reasonable for auditors to believe that scientists should not be distracted by the necessity of keeping one eye on the cash register while the other eye is on the microscope.“who know exactly where they are going and how they will get there”是定语从句修饰“scientists”的。

　　【翻译】审记员们完全有理由相信，那些确切地知道他们的目标和实现方法的科学家不应该由于一边做着科学试验一边需要盯着经济利益而分心。

　　The grand mediocrity of today—everyone being the same in survival and number of off-spring—means / that natural selection has lost 80% of its power in upper-middle-class India / compared to the tribes. (2000年真题)

　　【分析】句子主干为：The grand mediocrity of today / means that / natural selection has lost 80% of its power in upper-middle-class India. “everyone being the same in survival and number of off-spring”是插入部分，是对the grand mediocrity of today的一个补充说明。“compared to the tribes”分词短语作状语，修饰“that”引导的宾语从句，表示that引导从句所说明的情况在the tribes同样地发生了。(这里注意compared to与compared with的区别。compared to侧重于表达“相当于、等同于”的含义；compared with侧重于表达“与……相比较”的含义。)

　　【翻译】今天的普通大众，每个人有着同样生存机会和同样数量的后代，这意味着，自然选择在印度上流社会已经失去了80%以上的影响，在一些部落里情况也是一样。