现在分词&过去分词求解 谢谢谢谢！！

AmyGMAT

现在分词结构作定语修饰prep2-69
Sixty-five million years ago, according to some scientists, an asteroid bigger than Mount Everest slammed into North America, which, causing plant and animal extinctions, marks the end of the geologic era known as the Cretaceous Period.
A. which, causing plant and animal extinctions, marks
B. which caused the plant and animal extinctions marking
C. and causing plant and animal extinctions that mark
D. an event that caused plant and animal extinctions, and it marks
E. an event that caused the plant and animal extinctions that mark 正确E
我的疑问在B项 prep解释上说making前面要有逗号
现在分词作非限定性修饰成分，修饰先行词
我不明白的是为什么一定要加“，” making单独不可以修饰extinctions吗？
如果加上“，”我反而认为会造成修饰模糊，making可能会有修饰an Astroid 难道是因为现在分词做非限定性修饰成分，只能修饰它的先行词，而不能修饰主句的主语？？


下面一个是过去分词结构作定语
prep2-6
From studies of the bony house of the brain, which is the cranium, located in the back of the skull, come what scientests know about dinosaur brains.(全划线题)
A.From studies of the bony house of the brain, which is the cranium, located in the back of the skull, come what scientests know about dinosaur brains.
A错误的一个原因就是located因为没有紧邻修饰对象所以造成修饰不清
B.The knowledge that scientists know about dinosaur brains comes from studies of the bony brain, located in the back of the skull, that is, the cranium.
B项的错误也是因为located前面加了一个“，”没有紧邻修饰对象brain所以造成修饰不清
D.What scientists know about dinosaur brains comes from studies of the crandium, the bony house of the brain located in the back of the skull.


正确答案是D
prep笔记解释是：过去分词结构作定语，一定要尽可能紧邻其修饰词，用逗号隔离之后修饰的对象可能是临近的名词，可能是主语，也可能修饰后面的词，也可能做状语。


对于过去分词作定语的解释我明白，可是就是因为这点我不明白了现在在分词为什么一定要加上逗号呢？它不会造成过去分词可能产生的歧义吗？


OG12-1
The Glass House Mountains in Queensland, Australia, were sighted in 1770 by the English navigator Captain James Cook, by whom they were named supposedly because its sheer wet rocks glistened like glass.
(A) by whom they were named supposedly because its
(B) by whom they were named supposedly and their
(C) naming them supposedly since their
(D) who so named them supposedly because their
(E) who so named it since supposedly their
答案D
C As the object of a preposition and not the subject of the clause, James Cook does not work as the noun that the verbal phrase beginning with naming can describe; the preposition since loses the important causal logic of the sentence.
这道题本来我一开始选的C，naming是修饰JC这个人的，我想的就是JC使naming的先行词。
OG给出的解释有两点 1.the object of a preposition 2.not the subject of the clause
我对这第一点不是很理解，现在分词不是修饰先行词的吗？OG是说JC是在一个介词后面：by JC 。难道是说在介词后面就不能算是先行词，不能发出naming这个动作
是在是困惑


prep2-11
Nine months after the county banned jet skis and other water bikes from the tranquil waters of Puget Sound, a judge overturned the ban on the ground of violating state laws for allowing the use of personal watercraft on common waterways
A same
B of their violating state laws to allow
C that it violates state laws that allowed
D that it violated state laws allowing
E that state laws were being violated allowing

答案D
这里allowing没有和law分开，有一点原因我知道是因为修饰法律一般用现在分词
我的问题就是如果allowing前面加上“，”错吗？


问题比较多，但都是关于现在分词和过去分词修饰的问题。
是在太费解了
麻烦牛牛们帮忙指点一下~谢谢！！！

SAGA5

没有绝对的介词后名词不做先行词
这道题里 因为SLOTH在语法结构中的地位很低（不是主语也不是宾语的地位，而是某种修饰的意味）远比不上主语名词 所以相比起来没有理由不指主语而指SLOTH

AmyGMAT

Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of the Greater Antilles islands.
a.sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of
b.sloth, that they found in Puerto Rico in 1991, has been dated at 34 million years old, thus making it the earliest mammal known on
c.sloth that was found in Puerto Rico in 1991, was dated at 34 million years old, making this the earliest known mammal of
d.sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the earliest known mammal on
e.sloth which, found in Puerto Rico in 1991, was dated at 34 million years old, made the sloth the earliest known mammal of


这里OG对it指代不清的解释是：Because sloth is the object of a preposition and not the subject of the sentence，there is no reason antecedent for the pronoun it
这个和上面那个解释是如出一辙的，那么是不是就可以这么理解：在介词后的名词不能充当先行词？？

AmyGMAT

啊 哈哈 误会你意思了...

abjure

是啊，这题的理解和你一样。

AmyGMAT

呵呵 请问abjure你的理解是什么呢？
我按照OG的理解就认为是介词后的宾语不能做先行词，这点我只是暂时死记着，但也没找到合理的支持~

abjure

To AMY:  REPS 我没做，没有发言权。
关于OG 12-1 解释我的理解不是OG 想说的是，由于JC 在介宾结构里的名词，不是主句主语，所以naming 不可以修饰JC.  

OG12-1
The Glass House Mountains in Queensland, Australia, were sighted in 1770 by the English navigator Captain James Cook, by whom they were named supposedly because its sheer wet rocks glistened like glass.
(A) by whom they were named supposedly because its
(B) by whom they were named supposedly and their
(C) naming them supposedly since their
(D) who so named them supposedly because their
(E) who so named it since supposedly their
答案D
C As the object of a preposition and not the subject of the clause, James Cook does not work as the noun that the verbal phrase beginning with naming can describe; the preposition since loses the important causal logic of the sentence.
这道题本来我一开始选的C，naming是修饰JC这个人的，我想的就是JC使naming的先行词。
OG给出的解释有两点 1.the object of a preposition 2.not the subject of the clause
我对这第一点不是很理解，现在分词不是修饰先行词的吗？OG是说JC是在一个介词后面：by JC 。难道是说在介词后面就不能算是先行词，不能发出naming这个动作
是在是困惑

AmyGMAT

呵呵 谢谢~
可能是我太钻牛角尖了...这些问题实在是使我非常confused..
有时候对于选项里的错误又不敢不在意，万一哪天变成考点就虾米了~
哈哈
谢谢jtrchina，我再好好体会体会

jtrchina

Well,although such use causes ambiguous as we disscussed,it is only a trifle mistake that GMAT sometimes does not care.I bet that you must have such experience that the answer GMAC defined as the best sometimes contains many trifle mistakes.What GMAC want us to do is to select the tallest among the short.That means,the best choice is always not the PERFECT choice,right?
It is the logic meaning and some BASIC rules that determines the answer.Remember,do NOT expect the best answer to be perfect,without any small mistakes.

AmyGMAT

非常感谢jtrchina非常非常细致的解答
你说的surpassing容易造成ambiguous，这个我也想到了，可是在有的题里面就认为surpassing不会造成ambiguous
麻烦你看一下我贴出来的第一题的B选项 刨除which这个错误不看，prep笔记上还说making前面应该加“，”
这样问题就出来了，加上“，”后making的指代不会造成ambiguous吗？即可以指代an astroid 又可以指代extinction？
是这样吗？