雅思写作评分标准之一便是语法，7分语法要求考生能够熟练运用各种从句，error free，墨尔本文波雅思批改了上篇学生作文后发现大家对非限定性定语从句还是有很大欠缺。
非限制性定语从句
1)非限制性定语从句要用which, who, whose等词引起，它们可以修饰主句中的某个名词，也可修饰这个句子，起一种附加说明的作用，但不能用that引导。如把它省去，主句仍能表达明确完整的概念。
2)非限制性定语从句在修饰人时用who(whom)或whose；在修饰物时用which；在修饰整个句子时也用which。非限制性定语从句有时也可由when和where引导。
,none of
,all of ＋ which/ whose/ whom
,most of …
,many of …
, … of
l We toured a 300-year-old house.
l The exterior of the house consisted of logs cemented with clay.
We toured a 300-year-old house, the exterior of which consisted of logs cemented with clay.
l They own an original Picasso painting.
l The value of the painting is more than a million dollars.
l
They own an original Picasso painting, the value of which is more than a million dollars.
l
3)as引导的非限制性定语从句比较特殊，它既可放在主句之前，也可放在语句之后，此时as有“正如”之意。常用句型如下：
As is shown in…
As has been stated above…
As has just been proved…
As is well known…
As we know…
As has been pointed out…
经典例题：
He is always late, generally managed to annoy everybody.
A) which B) where
C) what D) that
is known to the world, Mark Twain is a great American writer.
A) That B) Which
C) As D) It
