21 be intended to modify them. e.g. Only in the past century was origami’s development, a ceremonial activity invented millennia ago, into a true art form taken place. (wrong) Origami—a ceremonial activity invented millennia ago—has developed into a true art form only in the past century. (correct)
名词性修饰语与关系代词
关系代词：which, that, who, whose, whom, where, when, 需遵守的规则：
1. who and whom must modify people 2. which must modify things. 3. That 不能modify people
4. Whose can modify either people or things: the town whose water supply was contaminated.
5. Which 和whom有时跟着介词，the canal through which water flows. The senator for whom we worked.
6. Who作为定语从句的主语，whom作为宾语 The security whom we met was nice.
7. That and whom当引导宾语时可省略：the movie that we watched last Friday was scary. The movie we watched last Friday was scary.
8. Where 可以修饰一个地点名词，比如：area, site, country, where 不能做?比喻?的含义，如果要修饰condition, situation, case, circumstances, arrangement 要用in which 而不是where.
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We had an arrangement in which he cooked and I cleaned.
9. When 可以修饰a noun event or time, such as period, age, 1987, or decade, 在这种情况下也可以用in which来代替。
Essential vs. non-essential noun modifiers
Noun modifiers are either essential or non-essential Essential modifiers 提供的necessary information to identify the noun or to attach the modifier to the noun from that point onward.
e.g. The mansion painted red is owned by the Lees.
这里必须用essential modifier，因为如果不用的话，则不知道说的到底是哪个mansion.(这也是essential modifier使用上的重点和难点，需要identify noun的时候就需要用essential modifier)
Non-essential modifiers 提供多余的信息，you do not need this information to identify the noun, since it is already identified in some other way.
e.g. This mansion, recently painted red, is owned by the Lees. ?this?已经指出了到底是哪个mansion, 所以后面的recently painted 是non-essential modifiers.
Put commas between non-essential and their nouns; Put no commas between essential modifiers and their nouns. 23
E.g. This mansion, which has been recently painted red, is owned by the Lees.
The mansion that has been recently painted red is owned by the Lees. Gmat不会把which和that当作是选择的唯一点，因为他们的使用 有分歧。
?who? can be used in essential or in non-essential modifiers.
Verb modifiers
动词修饰语修饰的动词，these modifiers answer questions about the verb, such as ?how, when, where, why? etc. The most basic verb modifier is an adverb. Other verb modifiers act in much the same way as adverbs.
从属连词包括because, although, if, unless, while, so that, while, and so on.这些从属联系必须和主句attach在一起。
有一些动词修饰语可以和动词以及动词的主语连在一起，这时一定 要注意make sure that the subject makes sense with the modifier. e.g.
现在分词： Whistling beat it, I lifted the weight. 介词+简单动名词：By concentrating, I lifted the weight. 不定式：To free my leg, I lifted the weight. I lifted the weight to free my leg.
24 Make sure that these modifiers have a sensible subject in the sentence. Wrong： The weight was lifted by concentrating. 注意不定式的用法和含义：
Infinitives of purpose can be used with unnamed agents in passive-voice sentence: the weight was lifted to free my leg. Just make sure that whoever does the lifting intends to free my leg.
An infinitive of purpose needs to indicate the purpose of someone.(不定式的主语需要指出到底谁是?目的?的主语)The boulder rolled to free my leg implies nonsensically that the boulder wanted to free my leg. (the boulder是to free my leg的主语，所以是不合乎逻辑的)
虽然动词修饰语不像名词修饰语那样必须遵守touch rule,但是其实它也必须跟所修饰的动词放在合理的位置，否则就会产生歧义：
The nameless symphony was at last performed, decades after it was composed, yesterday. (错误的将yesterday放在最后，没有合理的修饰performed) The nameless symphony was at last performed yesterday, decades after it was composed. (yesterday修饰的是was performed，合理的位置不会引起歧义) （引申：真题中很多情况下出现类似的错误，副词或介词短语是如何才能更好的修饰动词是个重点，很多时候是语感的问题）
Which vs 现在分词-ing形式
Which一定是修饰which之前的名词的，use which only to refer to the noun immediately preceding it---never to refer to an entire clause.
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e.g. The recent decrease in crime in our neighborhood has led to a rise in property values. (correct )
Crime has recently decreased in our neighborhood, leading to a rise in property values. (correct ) --ing的用法：
现在分词的使用非常灵活：
可以修饰名词：the changing seasons
可以修饰动词或他们的主语： I lifted the weight,whistling
可以修饰整个句子：Crime has recently decreased in our neighborhood, leading to a rise in property values.（表达前面一个句子的结果） 经常犯的错误是用which来代替前面一个句子，而不是名词。
Always test which clauses to make sure that the ?which? refers to the noun immediately preceding the ?which.?
第七章 时态、语气和语态
时态： 一般时态：
一般现在时：to express theeternal states or frequent events, general rule.Gmat比较偏爱一般时态，除非句子很明显的要求一个或更多复杂的时态 一般过去时： 一般将来时：
进行时态:to emphasize the ongoing nature of an action E.g.Sandy is playing soccer.