复合句——形容词性(定语)从句
定语从句的测试重点：选择正确的关系代词或关系副词。
切记：关系代词/副词一定要在从句中充当某种成分，即主语、宾语、表语或定语。指人时用who(做主语)、whom(做宾语)、whose(做定语);指物时用which或that;指时间用when;指地点用where;指原因用why。此外还要注意如下几个问题：
1.尤其要注意whose的用法
whose在从句中做定语，修饰名词。所以，如果关系代词后面紧接的是名词，且关系代词又不在从句中做主语或宾语，那么，这个关系代词就应该是whose。如：
Of course developing a system for helping students whose needs are out of the ordinary had been a necessary step in helping those students get into the world of public education.
It is perhaps not an exaggeration to say that we shall soon be trusting our health, wealth and happiness to elements with whose very names the general public are unfamiliar.
2.介词 + which的用法
如果从句中主宾成分齐全，考生便可考虑关系代词是否在从句中做状语，而状语通常用介词短语充当，于是可以得知，关系代词前面应有介词，再分析所给的选项，根据与名词的搭配作出正确选择。如：
Children are best served when schools contribute to shaping the solid foundation on which their future will be built.
However, the batteries from which they(electric vehicles) draw energy usually contain harmful chemicals, which become pollutants when the batteries are disposed of.
We are not conscious of the extent to which work provides the psychological satisfaction that can make the difference between a full and an empty life.
3.非限定性定语从句前面有逗号标志，按汉语习惯通常翻译成两个句子
切记：与汉语不同的是，英语中两个句子之间一般说来不能用逗号断开，而要用适当的连词或关系代词使它们形成从属或并列关系。据此可判断出逗号后面一句应由起连接作用的词开头。注意：有时关系代词前面还有其他附加成分。如：
Biologists believe that rainforests are the home of perhaps half the world’s biotic species, about five-sixth of which have not yet been described and named.
There are two spare rooms in the building, neither of which has been provided with modern facilities.
4.as 与which用作关系代词的区别
(1)as与the same, such, so, as等关联使用。如：
As the forest goes, so goes its animal life.
(2)as和which都可以引导非限定性定语从句，但as在句中的位置比较灵活，可出现在句首、句中、句末，而which只能出现在句末，尤其是当先行词是整个句子时。如：
As is true in all institutions, juries are capable of making mistakes.
As is generally accepted, economic growth is determined by the smooth development of production.
常见的这类结构有：
as has been said before, as has been mentioned above, as can be imagined, as is known to all, as has been announced, as can be seen from these figures, as might/could be expected, as is often the case, as has been pointed out,
as often happens, as will be shown等。
5.关系代词that与which用于引导定语从句的区别
(1)如果关系代词在从句中做宾语，用that, which都可以，而且可以省略;
(2)先行词是不定代词anything, nothing, little, all, everything时，关系代词用that;
(3)先行词由形容词最高级或序数词修饰或由next，last, only, very修饰时，用that;
(4)非限定性定语从句只能用which引导;
(5)关系代词前面如果有介词，只能用which。
6.but做关系代词，用于否定句，相当于who…not, that…not
这个结构的特点是主句中常有否定词或含有否定意义的词。如：
There are few teachers but know how to use a computer.
There is no complicated problem but can be solved by a computer.
