练习：

1）Make primary care more attractive to medical students by forgiving student loans for those who choose primary care as a career and reconciling the marked difference between specialist and primary care physician salaries.（200912）

解析：没有主语的祈使句。By后面的方式状语甚长，实际上有forgiving和reconciling两个动词共同当by 的宾语，those后包含一个who引导的定语从句。

2）This is especially true in agriculture, where sustainable development is often taken as the sole measure of progress without a proper appreciation of historical and cultural perspectives.（200812）

解析：This is especially true [ in agriculture, where sustainable development is often taken [as the sole measure of progress [without a proper appreciation of historical and cultural perspectives]].]

主句是this is especially true.理解关键是对状语部分所含的定语从句的把握。状语分三个层次，绿色为第一层，红色为第二层，蓝色为第三层。

3）The key will be to abandon the rather simple and static measures of sustainability, which centre on the need to maintain production without increasing damage.（200812）

解析：主干为the key will be. 关键理解which引导的非限制性定语从句。

4）Many Europeans now apparently view the U.S. the way many Americans view Mexico-as a cheap place to vacation, shop and party, all while ignoring the fact that the poorer locals can’t afford to join the merrymaking. （200806）

解析：Many Europeans view the U.S.是句子主干。The way是状语，省略了in. as a cheap place to vacation充当方式状语。all while ignoring 是独立主格，其后the fact后跟同位语从句。

5）So we’ve contrived various justifications that turn out to be half-truths, prejudices or myths. It actually doesn’t matter much whether Aaron and Nicole go to Stanford.（200806）

解析：本句主干为we’ve contrived justifications， justifications后that引导的定语从句，是一个主系表的句子。

6）Crippling health care bills, long emergency room waits and the inability to find a primary care physician just scratch the surface of the problems that patients face daily.

解析： bills, waits and the inability是主语，各自带有自己的定语，problems后有一个定语从句。

7) Not necessarily because of the promise of free or reduced price phone calls (which experts point out is misleading for the average business), but because of the sophisticated voice services that can be exploited by the remote worker—facilities such as voicemail and call forwarding, which provide a continuity of the company image for customers and business partners.（200912）

解析：Not necessarily because of the promise of free or reduced price phone calls ) (which (experts point out) is misleading [for the average business]), but because of the sophisticated voice services( that can be exploited )[by the remote worker—facilities such as voicemail and call forwarding], which provide a continuity of the company image (for customers and business partners).

括号内Which is misleading是个限制性定语从句，services后面是定语从句，其后把包含一个which引导的非限制性定语从句。

    评点：

    定语从句相当于形容词，修饰句子中的名词或代词，在句中作定语。被定语从句修饰的词称为先行词。定语从句分限制性定语从句和非限制性定语从句两种。

先行词一般是名词和不定代词，数词也可以作先行词，人称代词也同样可作先行词。先行词在从句中作主语时，从句谓语动词的数由先行词定。由于关系词在从句句子中充当了成分，其意思就是先行词的意义，所以在从句中不能重复其意。

关系代词可以做主语、宾语、定语和表语：who, whom, which, that, whose, as，but, than

关系副词可作状语：when, where, why

确定关系词的步骤：

(1)先找关系词，看先行词指的是什么。

(2)看关系词在从句中所充当的成分。

注：

1)      Who主要指人，在口语中可替代whom作宾语。

2)      Whom主要指人，在定语从句中作宾语，口语中可用that或who代替。

3)      Which一般不指人，但在以下三种情况可指人

先行词是婴儿或儿童；先行词为集体名词；先行词强调每类人的性格、素质、地位或职业。

4）下列情况的关系词宜用that而不用which

　先行词被形容词最高级、序数词、数词几种词修饰或被only、any、few、little、  no、all、one of等修饰时；先行词为all、much、little、none、few、one、something、anything等不定代词时；先行词中既有人又有物时。

　　5）下列情况的关系词宜用which而不用that

　  在非限制性定语从句中；在关系词前有介词时；当先行词本身是that时；当关系词离先行词较远时。

　  6）whose作关系词既指人又指物，在从句中作定语。

　　7）关系代词as, 在从句中作主语、宾语和表语。

　　8）关系副词when与where、why、that

　　when 指时间 = in / at / on / during which

　　where指地点 = in / at / from / which

　　why指原因 = for which

    9）the way, the day, the time, the moment, the instant等后面，关系词that, when, at which或in which常常省略。

　　(10) 定语从句与同位语从句的区别

定语从句引导词被称为关系词，that充当主语、宾语、表语。有时可省略。同位语从句引导词被叫做连词，that不能充当任何成分，不可省。